It promises to reshape our relationship with the online world - or turn us all into cyborgs, invading each other's privacy with careless abandon. Say what you like about Google Glass, it's certainly proved a talking point.

I've spent the last 24 hours trying out Google's wearable computing device, talking to people who are developing apps for it, and gauging the reaction of onlookers.

The product - which is still a long way from being ready for consumers - has been in the hands of developers for a few weeks now, and many of them have converged on San Francisco for the Google I/O conference.

When I had a couple of hours to try it out I found that, like any new interface, Glass had some rough edges. The screen looks rather bigger and more useful than I'd expected, like a reasonable-sized TV seen across a room. But you need to learn a series of touch commands on the arm of the glasses, and often I found myself stuck halfway down a long series of menus, swiping back and forth and getting nowhere.

At the moment, there is a limited amount you can do with Glass - it's like a smartphone without any apps - and for many of the functions you may be constrained by the quality of the 3G connection on the phone to which it is paired. You may also feel a bit daft walking down the street and shouting to yourself, "Do I need an umbrella tomorrow?"

The voice recognition in the device is very smart - and even seems to understand my English accent - but again, once you leave a strong wi-fi connection, everything seems to become a little harder. And what about those privacy worries inherent in a device which can be recording without your subject knowing?

When I took Glass for a stroll on the beach overlooking the Golden Gate Bridge, the elderly dog walkers there were more amused about a strange Brit talking to himself than anxious about their privacy, although the majority felt the whole idea was rather more creepy than cool.

Where Google's big idea impresses most is as a camera. Because it captures exactly what you see, you get the kind of pictures you often miss with a camera you have to ready for action. And when it comes to video, the footage is much steadier than what you often see from a shaky camera phone.

We began our filming by visiting the world's most enthusiastic early adopter, the blogger Robert Scoble. He's certainly mastered the art of Glass photography - as you can see from his picture of us filming him.

Despite his promise never to go a day without the product - or something similar - he has a few words of caution. The price needs to be right, he says, and the product has to be able to do a lot more if it is to appeal to a wide audience.

By the sound of it, there will soon be plenty more apps. Developers big and small are in San Francisco, showing off their projects. Rajiv Makhijani and two friends who won a Glass hackathon, are now developing a social gaming idea, which sounds to me like Foursquare meets match.com. Bigger players, including Twitter, Facebook and Evernote are also thought to be working on apps.

What strikes me in San Francisco is the sheer fascination and excitement of many people when they see Glass for the first time. It feels to me that we are ready for a new way of interacting with the web.

Google Glass may be clunky, and it certainly isn't going to win any fashion awards. There are serious debates to be had about its legal and social implications. But we may look back 10 years from now, and say this was the moment when wearable computing stepped out of the sci-fi films and into real life.

The device in question is an accessory for the Raspberry Pi, the cheap barebones computer aimed at getting children coding. And, on reflection, the sheer nightmarish complexity of making it work may be exactly the point.

The camera, which I've been testing for a couple of days, is all of a piece with the Raspberry Pi aesthetic - a tiny lens on a chip smaller than a postage stamp. The accessory, released today, is like the Pi itself in that it makes few concessions to modern expectations of consumer products that you plug 'n' play.

You connect it to a port on the Pi and start working out what to do next because it's not as if there's a button on it to press to take a picture, or even a pre-installed programme on the Pi desktop to operate the camera.

In my case, I emailed a few people in the Raspberry Pi community and got a list of instructions. You need to connect your mini computer to a monitor, start it up, then open a terminal window and type in this command: /opt/vc/bin/raspicam -o mypicture.jpg

A window opens on the monitor showing what the camera is seeing and, after what seems a random number of seconds, a picture is taken. Next, you have to work out where that picture - or video because another command allows you to record moving pictures - is stored. Then you have to work out how to get these files off the Raspberry Pi to somewhere you can edit or distribute them.

After a certain amount of cursing - and further consultation with a friendly Raspberry Pi guru - I managed to achieve this, saving a few pictures of myself, the dog and a somewhat reluctant 14-year-old son.

None of my Raspberry Pi photos were up to much and I won't be entering the Pi photography competition that has been launched to celebrate the arrival of the camera. (By the way, once you have got to grips with the various commands, you can do all sorts of clever things with the camera, from an "old master" effect, to black and white or negative shots.)

But I still found the whole lengthy process rather satisfying. Instead of turning a camera on and pressing a button, I'd been forced to think about the software behind digital photography and muddle my way through.

And that is why Raspberry Pi is such an interesting and challenging idea. It forces you to explore how computers work and in that process learn some useful skills.

As someone who is anything but a digital native, I find this stuff hard. Hopefully it will be a lot easier for those at whom this is aimed.

In my view, the packaging and presentation of the Pi have been just a little too challenging so far for many of the target audience: children, their parents and teachers. Once they've assembled the necessary peripherals - a monitor, a mouse, a keyboard, cables - and got the thing booted, it is probably unclear to many what on earth they are supposed to do next.

But this is why the camera is such a useful addition to the project. It may be difficult to get your head around at first but you end up with an output that everyone can understand - photos or videos.

A couple of months ago, I helped judge a competition for schools finding imaginative uses for the Raspberry Pi. There was a lot of ingenuity on display and, now that there's a camera for them to play with, I'm expecting to see a lot more clever Raspberry-flavoured ideas emerging from Britain's classrooms.

The answer is it won't - in the short term at least - but that's not the aim.

This is all about reinforcing BT's broadband business and making its customers less likely to head elsewhere.

More and more consumers are choosing to get their phone, TV and broadband services in one package - with Sky an obvious choice for many.

The satellite broadcaster has been Britain's fastest growing broadband supplier in recent years, winning many of its new customers from BT.

Now a well-funded and familiar brand is advancing onto Sky's territory, armed with some top class sport.

Sky may be relaxed - after all it's seen the likes of ITV Digital and Setanta try and fail to do something similar.

But for consumers there's the prospect of more choice and lower prices - which looks like good news.

One thing was, however, clear. This company is growing in all sorts of ways, and with that comes growing pains.

After all those anecdotal reports that "none of my friends use it anymore", and various research firms hinting at falling user figures, the hard numbers say Facebook is still expanding. Monthly active users rose to 1.1 billion, meaning 100 million new users had arrived in the last six months.

Now many of them will be in developing countries - after all so many people have already joined in places like the US and UK that Facebook is reaching saturation point. But the company insists, that contrary to reports, it is still growing in both of those countries.

In the UK, user numbers hit 33 million in December, and I'm told there has been a modest increase since then. In the US, there has also been a rise from December's 174 million monthly users, though it looks like the growth story there is nearing its end.

There has been a decline in use of the network on the desktop but that was more than made up for by the growth in mobile use, where advertising returns have proved higher. And that rapid transformation of the firm into a mobile advertising business will be the most encouraging aspect of the figures for anyone who was brave enough to buy Facebook shares at their sky-high IPO valuation last year.

Mind you, there's growth too in the cost of running the business, as more staff are taken on. The UK operation is among those expanding rapidly, as I found out this week when I met the engineer in charge of one of the firm's most important ventures, Graph Search.

Lars Rasmussen has moved to London to head up an expanded engineering operation, and he is in the process of recruiting another couple of dozen people to work mainly on the search project. (How easy that process proves will be an interesting test of the computer science skills available in the UK.)

Each of the recruits will then spend four to six weeks at a boot camp in California, learning how Facebook writes code and attending lectures by its top executives.

That sounds like an expensive process and a contrast to the early days of a business where Mark Zuckerberg just called up a few friends for all-night coding sessions fuelled by pizza.

But if the London team can then help take Graph Search to the next stage, where users will be able to comb the network's newsfeed for all kinds of information, then it will have been a worthwhile investment. So far, Facebook's limited search bar has not done anything to worry its rivals. But if it becomes a conduit to breaking news, then the likes of Twitter may have to sit up and take notice.

Like an awkward teenager, however, Facebook is finding that growing up can be painful. Yesterday's story about its refusal to remove horrifying decapitation videos, followed by a rapid U-turn, is a case in point.

Like so many other web giants, Facebook just wants to be seen as a technology platform enabling its users to do all sorts of cool stuff without any interference. But it has grown into a massive media player, where more than a billion people - many of them under 18 - come in search of entertainment.

That means a constant spotlight is being shone on the firm's policies, with parents and regulators increasingly worried about an environment where young people now spend so much time. Welcome to adulthood, Mr Zuckerberg.

If you travel on trains packed with commuters staring at tiny mobile phone screens rather than books, or wander along high streets now devoid of bookshops, you might think it was in a sorry state.

But the Publishers' Association annual statistical digest, published today, seems to paint a different picture.

The industry had a record year for sales, up 4% to £3.3bn. 2012 was the year when the digital revolution really took hold, with sales up 66% to £411m and fiction e-reading growing even faster, up 149%.

As for the physical book, long thought to be under threat from all those Kindles, Kobos and Nooks, reports of its demise may be premature. Sales fell just 1% to £2.9bn, and in some genres, notably children's books, sales actually rose.

The figures also show that the pace at we're switching from physical to digital books varies according to the type of title. Apparently, 26% of fiction sales are digital, whereas for non-fiction books the figure is just 5%, and for children's titles, 3%.

Why? Well perhaps for fiction it is only the words that matter, and they can be rendered as well or better in digital form, whereas for something like a glossy cookery book or an illustrated children's book, the physical object still delivers a much better experience.

What does this mean then for the pace of publishing's digital revolution and its impact on readers and authors?

A few weeks ago Michael Serbinis of the e-reader maker Kobo told me he reckoned that 90% of reading would eventually be on digital devices.

You won't be surprised to hear that Richard Mollet of the Publishers' Association is betting on a lower figure - somewhere between 30% and 50%. But however rapid the shift to e-readers, publishing seems to be weathering digital climate change better than some other media industries.

But what about authors? I was surprised to hear from JoJo Moyes - a bestselling writer of women's fiction - that nearly half of the sales of her latest book were in a digital format. And each digital sale earns her a few pennies more than the royalty she gets from a physical book sale purchase.

Mind you, not all authors are happy - they point to the much lower costs of producing digital books and wonder how publishers still justify taking such a large cut.

The publishers' response is that they have to spend large sums defending authors from the threat of piracy.

JoJo Moyes has some sympathy with that argument: "I've got a Google alert set up and every day it tells me about a new torrenting site offering free copies of my book. I pass them on to my publisher to deal with. "

Still, neither publishers nor authors seem to have seen their incomes damaged significantly by either piracy or the wider digital revolution. Readers, meanwhile, have a wider choice, and perhaps the prospect of lower prices - although many will grumble that e-books should be a whole lot cheaper.

For bookshops the news is not so good. Independent book stores continue to close, as readers turn to online giants like Amazon for both physical and digital books.

That is making our high streets just a little less interesting, so it's a vicious circle where going out and browsing for books or anything else becomes less attractive than sitting at home and shopping online..

But overall, 2012 seemed to show that the British public still loves books in all their variety, and is prepared to pay to enjoy them.

We hear plenty of doom and gloom from the old media industries about the ravages of the digital revolution - but publishing seems determined to look on the bright side.

But what is interesting about the case of Ramzan Karmali and his missing wallet is that, to put it politely, his network is minuscule.

Ramzan is a BBC business producer, a cheerful former City trader who sits opposite me in Broadcasting House. On Thursday evening however he wasn't so cheerful when he got off the suburban train home to find he'd left a bag containing his wallet behind.

Now Ramzan isn't the most prolific user of social networks - on Twitter he has just 160 followers - but he thought it was worth trying to send out an alert. So he tweeted this:

Now of course it was extremely unlikely that any of his followers would have been on that train - but he followed up with this:

And a number of his friends (not me, I'm ashamed to confess) took the hint and retweeted his appeal. So that quickly multiplied the audience for his tweet to several thousand people.

Late that night, Ramzan got a message from someone with the Twitter handle @flipchartqueen. This was Sheila Thorne, who had been sitting opposite him on the train. She'd spotted the lost bag, taken it home and called the police.

Then, after several hours of hearing nothing back, she googled Ramzan, whose name was on the credit cards in his wallet.

The following day, they met in Central London, Sheila handed over the bag, and Ramzan presented her with a box of chocolates.

"Five years ago this would never have happened," he says. "A combination of honesty and technology got my bag back."

Now, despite the many learned treatises written on the network effect, it remains unpredictable - what decides whether a joke goes viral, or an appeal for help remains unheard? In this case, it appears to have been a combination of Google and Twitter that combined to bring Ramzan's plea to exactly the right audience.

But there is another person my colleague needs to thank for making the spread of vital information work so smoothly.

Twenty years ago today the nuclear research centre CERN put out a press release announcing that it was making freely available something called the World Wide Web, "a global computer networked information system".

Its creator, Tim Berners-Lee, was determined that the web should be an open system, not a series of walled gardens controlled by governments or corporations.

And, while we can argue over just how open the web remains, if Ramzan's tweet had been locked inside something like the Compuserve network of the 1980s rather than out on the web, then Sheila might never have seen it.

Luminaries past and present from across the UK's computing industry had gathered to mark the 75th anniversary of the Cambridge University computer laboratory.

But there was also one nagging question. Why does a city and a country which have played such a huge part in the history of the computer, still produce so few world-class technology companies?

A strange question to ask, perhaps, in a lecture theatre packed with successful alumni of the lab, some from companies like ARM and CSR which have thrived in Cambridge. After all, this is a city where academia and business have combined very fruitfully in the past two decades.

But in a lecture on what he's learned about innovation, Mike Lynch - who's the founder of another Cambridge technology success story, Autonomy - bemoaned the fact that all the brilliant work done by the university's scientists had failed to translate into many big hitters in the FTSE-100.

Just one UK computer business had made it into the FTSE, he told us, and that was Sage, the Newcastle-based accountancy software firm. "Our universities are second to none," he said. "But they're failing to translate the gold coming out of them into economic growth."

(It now strikes me that Dr Lynch is ignoring the fact that the chip designer ARM is in the top third of the FTSE-100 - but maybe he doesn't count it as a computing company?)

He suggested that many companies with excellent technology got to a certain stage and then they or their backers lost confidence, selling up to American firms. We were, he suggested, producing great R&D labs for overseas firms to exploit rather than going on to turn high quality research into products for global markets.

Dr Lynch, of course, eventually sold Autonomy to America's Hewlett Packard and is now embroiled in a row over just what his company was really worth. But his point was that more firms needed to stay independent long enough to create a lasting infrastructure in Britain, even if they ended up in foreign ownership.

Others in the audience then joined a discussion about the way forward. Lord Broers, a distinguished engineer and former vice-chancellor of Cambridge University, was worried by how little we spent on research and development as a country compared to rivals - 1.7% of GDP in the UK, as compared to 2.8% in Germany and 2.9% in the United States. "We're underspending by billions, mainly in industry," he said.

There were the usual worries about a gap in capital for technology companies - plenty at the start, then very little when they wanted to make the leap into the big league. And there were calls for government to to think more about using its own procurement budgets to help UK firms in the way the US did - for the different tech clusters, from Cambridge to Bristol to London's TechCity, to collaborate better; even for The Sun newspaper to start celebrating computer scientists on page three.

Mike Lynch's main concern, however, was about the teaching of STEM subjects - science, technology, engineering and maths - in secondary schools where he felt we were falling behind. He cited as an example the scarcity of girls taking A-Level physics.

We had brilliant graduates coming out of places like the Cambridge computing laboratory, he said, but that supply could dry up, and we needed a wider hinterland of skilled people. Those worries about a skills gap opening up are now commonplace amongst many in Britain's hi-tech industries.

But Cambridge, the birthplace of computers from the Edsac to the BBC Micro, has at least produced an attempt to address that problem with the Raspberry Pi, which aims to inspire a new generation of computer scientists.

That continuing spirit of innovation should provide some cause for optimism that we can find ways of turning world-class science into world-beating businesses.

But this time investors saw just enough in the results to cheer them up a bit.

The rise in iPhone sales in particular provided some evidence that the most lucrative product in Apple's history might go on adding to the company's enormous cash pile.

The CEO, Tim Cook, while stressing that Apple had always met its own estimates, did acknowledge that others had been disappointed recently - and seemed eager to calm investors' fears.

But he also made it clear that the next few months will be a lean period, with teams working hard to introduce new products "this fall and throughout 2014".

Apple's boss is promising that innovation isn't over at his company - but investors' patience will be tested through the summer.

Over the course of its history, the London Marathon has seen more than half a billion pounds raised for charity and most of this year's 37,000 runners were raising healthy sums for their chosen causes.

Many will have used web-based donation services like JustGiving and Virgin Money Giving, which are making an ever greater contribution to fundraising. But a London technology start-up called Believe.in says it has a plan to make the whole process even more efficient.

Believe.in has what looks at first a very simple, indeed unbelievable, pitch: it will pass on 100% of the money you raise in donations and Gift Aid to your chosen cause.

In that, it contrasts its approach with that of other services, notably JustGiving, which has most of the online giving market. It takes a 6.3% cut - 5% from the donation plus a share of the Gift Aid and credit card fees.

JustGiving is a business with staff to employ and investors to keep happy, and it has done a good job for charities by promoting the idea of online giving. Whether its profit margins are too high is a matter for debate - though it should be said that profits were actually down last year.

So how can Believe.in afford to charge nothing? After all, it isn't a charity. In fact, it is a well-funded start-up backed by some very savvy investors including Index Ventures and Greylock Partners.

When I met one of the co-founders, Matthias Metternich, he was keen to stress that the company was about far more than delivering a more efficient payments system. "It's about charitable identity," he explained. "It's about what does it mean to be a charitable person."

Believe.in aims to deliver a range of web services to three groups - charities, businesses looking to expand their philanthropic activities, and ordinary individuals involved in fundraising. It plans a "freemium" model. Charities will get something for nothing but will then pay for more sophisticated services.

I was sceptical about how big the market for this idea was but Metternich told me there was a huge number of smaller charities without any idea of how to build an online presence. "They're asking things like how do we process payments online, how do we build a community, how do we handle social media?"

Overall, the charity sector raised £58bn last year but smaller charities were caught in a cycle where they raised money one year, then spent a lot of it on attracting donors to keep them going the following year. "Small charities have never had access to the kind of technology they need to make the process more efficient," he explained.

It is clear that the charity sector is ripe for a digital revolution. A study last year found that while 50% of people in the UK now shop online, only 2% were donating on the web, and the levels of investment by charities in their web operations were tiny.

Believe.in is part of a wider movement in the UK's tech community to change this. But it faces two big challenges - the dominant position of JustGiving as the recognised brand for online fundraising, and the inertia of the charity sector. Change comes slowly in the charity sector, so the investors backing believe.in may need to be patient.

Well from today there's an app for that.

The British Museum is launching applications on Apple and Android devices which are designed to give users a virtual tour of the exhibition, with all kinds of multimedia add-ons. It's part of a trend which sees cultural organisations using digital technology to reach new audiences.

The app features interviews with experts, photos of the exhibits, and an interactive timeline which takes you through the story of life in Pompeii and Herculaneum before and after the eruption of Vesuvius in 79AD.

Another innovation in the museum's digital offering is Pompeii Live, which will bring the exhibition, along with experts like Mary Beard, to more than 250 cinemas on June 18th.

That's an approach which has been pioneered in the UK by the National Theatre, which now regularly broadcasts plays to UK and overseas cinema audiences in its NT Live programme.

The National also reaches millions of people by distributing video content about its work via the iTunes U platform, and offers schools digital resources such as interactive whiteboard lessons featuring performances and discussion of plays.

In the US, another cultural digital experiment launches today, with the arrival of the Digital Public Library of America. It will feature all kinds of artefacts and historical documents from libraries and museums, available free for a global audience to inspect online.

All of these institutions are trying to achieve the same thing - delivery of a cultural experience to people who may never be able to come through their doors. But here's the difficult bit for arts administrators: how do the economics stack up? After all, digital content can be expensive to produce and distribute.

While many of these ventures are free, the British Museum has chosen to charge for its apps. On Android phones and the iPhone you will pay £1.99, and on an Apple iPad £3.99. While it is getting harder to get users to pay for apps - except through those notorious in-app purchases - the museum may find it is on a winner with Pompeii. After all, 120,000 have already paid £15 each for tickets to the exhibition, and the catalogue will set you back £30.

Tim Plyming, head of digital at the British Museum, says the app fits fits into an overall strategy "to increase access and deliver content to a very wide audience both nationally and internationally". He says it has been produced on a "a cost recovery basis" but is a pilot for potential income generation in the future.

In harder times, cultural organisations are trying to do two things: boost their audiences and balance the books. Many of them will be watching the Pompeii app's progress up the charts to see if this kind of digital venture offers one solution.

In a briefing with technology journalists, the woman who is one half of the dynamic duo running Facebook - the other of course being Mark Zuckerberg - made it clear that mobile was now the company's be all and end all.

"To say that mobile is important to Facebook is the under-exaggeration of all time," she told us. For the first time last quarter, users had spent more time with Facebook on their mobile phones than on the desktop.

She admitted that the company had been late to get its mobile operation right and had made plenty of mistakes. The firm got underway in 2004 just before the mobile internet revolution took off - Mr Zuckerberg has said if it had been a couple of years later, he would have started it as an app - and the transition over the past year had not been painless.

"We made a pretty big bet on HTML5, hoping we could build our applications once and it would work on all the different operating systems," Ms Sandberg said.

But that had failed - and they had to start again building separate apps for Apple's iOS and Google's Android.

Now though, the new Facebook Home - in effect a skin you can install to turn an Android phone into a social networking device - seems to be right at the centre of the mobile strategy. Ms Sandberg said the openness of Android allowed developers and users to tinker with it in a way which was impossible with Apple's operating system, so Facebook Home wouldn't be coming to the iPhone.

When I asked whether this meant she would recommend users to go for Androids rather than iPhones, she was quick to stress that Facebook still worked very closely with Apple, and we'd soon see some elements of Home in the iOS app. "But we are certainly saying, Facebook Home is the most immersive and best state-of-the-art Facebook experience you can have."

And, as Facebook is an advertising business, the Facebook Home experience will have ads integrated into it - even when the phone is locked. "Putting ads there is exactly the same as putting ads into your newsfeed," she explained.

And while Facebook prides itself on being able to offer marketers targeted ads - such as 24- to 35-year-olds in Essex interested in motorbikes - she said there was a much simpler proposition behind its mobile advertising proposition.

"The size of the audience makes this - the phone - a mass medium. It's as important to a marketer as TV." She hammered the point home: "This is as important - if not more important - than television."

Having noticed adverts becoming more prominent in both the new newsfeed and in Facebook's various mobile apps, I wanted to know whether Ms Sandberg thought there was a danger of users reaching saturation point.

She said Facebook monitored this by having a group which was shown no ads. They were then compared for their engagement with those who got the standard advertising experience. "So far, we're very pleased with the results."

A year ago, Facebook on a phone was an ad-free experience, which was causing some concern to investors. Now the company has become a big player in this new advertising market, but the chief operating officer was keen to reassure users that there were limits.

"Our goal is not to increase the number of ads you receive but to increase the usefulness of those ads to you."

The future of Facebook, then, is as a company fully integrated into your mobile experience, serving adverts that you enjoy as much as an update from your friends. If the Sandberg/Zuckerberg dynamic duo can pull that off, then the huge valuation put on their company last year may not look so outlandish after all.

Actually, what I had was 0.53 in Bitcoin, the virtual currency whose wild gyrations over the last 24 hours have raised questions about its long-term viability.

I got my Bitcoin a couple of weeks ago, because I was making a radio piece about the currency. My mission then was to work out how easy it was to get and then spend Bitcoins - and I eventually ended up with a rather expensive pizza, ordered via an American site and delivered by a London chain.

The whole cumbersome process of getting and spending the currency invented in 2009 by a mysterious Japanese (or possibly American) man called Satashi Nakamoto convinced me of one thing - that Bitcoin was not yet much use except as a means of speculation.

The only reason to get hold of Bitcoins right now is because you think they might be worth a lot more in a few hours or days. Now if you bought into the market back in January when you could get one Bitcoin for $15 (£10) you'd have been pretty smug yesterday when the price hit a new high of $260 (£170).

But if you were one of those who found out about Bitcoin from the mass of recent media and bought at yesterday's peak, then you've learned a valuable lesson - like tulips in the 17th Century and London houses in 1988, prices can go down as well as up.

There have been all sorts of explanations of what caused yesterday's crash - from a problem at the main exchange to a strange incident in which someone called Bitcoinbillionaire apparently started giving away large sums on the social news site Reddit.

A likelier reason is our old friends Greed and Fear combining to inflate and then depress prices as all those new arrivals crowded into the market.

All this talk of a Bitcoin bubble has annoyed the true believers - an interesting mixture of libertarians and cryptographic specialists charmed by the idea of a currency that embodies many of the open and virtually ungoverned principles of the internet itself.

They maintain that the key feature of Bitcoin is that the supply can never exceed a certain number - 21 million - and that it has recovered from previous crashes when its demise was predicted.

What is true is that we are seeing a fascinating experiment in what a currency of the future might look like. But unless and until Bitcoin can be used to buy a sandwich, or be accepted by your friends when you pay them back for a restaurant meal, then it is likely to remain just a playground for geeks and gamblers.

But when she visited London, the focus was bound to be on one of the worst decisions HP has ever made - its acquisition of the British technology firm Autonomy in 2011.

Last November HP took an $8.8bn (£5bn) write-down on the value of Autonomy, a business for which it had paid roughly $11bn. At the same time the firm and its CEO launched an extraordinary attack on the Cambridge-based software firm's former management team, accusing them of misrepresenting the value of the business and of accounting irregularities.

Mike Lynch, the firm's founder, rejected the charges and accused HP in turn of destroying his software business through its own ineptitude. The whole affair is now in the hands of the regulators and the courts. So was it wise to pick such a public fight last November?

"It was necessary," Meg Whitman told me this morning. She repeated HP's claims to a US court, saying "there had been very serious strategic misrepresentations, accounting improprieties and when we understood what had happened we had to explain to our investors".

Obviously the huge write-down had to be explained somehow to investors. But the suspicion among some has been that the charges of impropriety were a convenient smokescreen to cover a simple truth - that HP had paid far too much in its desperation to land the deal.

Even on the day the deal was announced, I wrote that one extremely sceptical analyst told the CEO Leo Apotheker he was paying "a fantastic price".

Meg Whitman was not in charge at the time but was on the board - and in our interview she came pretty close to admitting that HP had overpaid with or without any accounting shenanigans. She insisted a "big chunk" of the write-down had been due to what emerged about the company after the purchase. But what about the rest of it?

One person close to the former management of Autonomy said even HP's allegations about questionable accounting only added up to $100m in misclassified sales: "It's impossible to get from a revenue misclassification of $100m dollars a year to a writedown of $5bn."

Last week, one HP figure did pay the price for the disastrous deal. Chairman Raymond Lane resigned, and that gives the CEO some breathing space.

Meg Whitman has always said it will be a long job turning around HP, but she told me she'd made a lot of progress. She'd won the "hearts and minds" of HP's 300,000 strong workforce to her strategy, the company had "the best product line we've had in a decade", while innovation was "alive and well".

If so, that message has yet to be communicated to the outside world. It's hard to think of any standout products that would get customers thinking of HP as a great innovator. The CEO admitted customers hadn't said that for a while but promised that in the next six months that would change, with its new line of Moonshot servers and its enterprise security software: "In six months, I bet people will say 'wow, I didn't know HP had all this'."

The most obvious change she's made since taking over is to squash the idea that HP should spin off its core PC business, which has been badly left behind in the move to mobile computing.

She recognised the need to compete in a world which has been transformed by always-on touchscreen devices of all shapes and sizes. So was there going to be a mobile phone?

"We want to. What we haven't figured out yet is how to do that without it just being a me-too product and losing a lot of money, which I'm not interested in doing."

Given its recent history, you can see why HP's boss might be cautious about spraying money around to little effect. But if she's to make the business a technology leader again, rather than managing its decline, Meg Whitman needs to come up with a standout product pretty soon.

For the last few years, the social network has alerted me and many others to all kinds of breaking news, but it was a traditional news source, the Press Association which flashed this line at 12.47 pm:

"Baroness Thatcher died this morning following a stroke, her spokesman Lord Bell said."

The first tweets I can find were at 12:48 BST, within seconds of that PA flash - among them my BBC colleagues Stuart Hughes (@stuartdhughes) and James Pearce (@pearcesport) Strangely, the Press Association's own Twitter feed (@pressassoc) did not pass on the news until 12:50 BST.

But from then on, Twitter was consumed by the news, and was the place many came to offer tributes - or to fight over the Thatcher legacy.

Among the first tribute tweets I spotted was this from a Conservative MP Therese Coffey at 12:55 BST: "RIP Margaret Thatcher. You transformed our country for the better, putting Great back in Great Britain, & helped open the Iron Curtain."

Lord Sugar - who was a Labour minister under Gordon Brown - explained how the Iron Lady had transformed the business world:

Many more followed, from presidents and prime ministers past and present, and all manner of celebrities.

Even five years ago politicians and other well known people might have issued statements or rung broadcasters. Now it seems that they see Twitter as the fastest and most effective medium to share their thoughts with the world.

But as supporters tried to sum up the Thatcher legacy in 140 characters, a number of less enthusiastic voices were making themselves heard.

Labour tweeters urged party members to be respectful - but the Respect MP George Galloway was in no mood for restraint, tweeting "Tramp the dirt down". There was instant, furious reaction, and this and a number of other shouting matches filled the social network with bile for some hours.

But Twitter was also the place to find more illuminating information - from links to obituaries to data about the UK's economic record under the Thatcher premiership.

While much of Twitter's global audience seemed fascinated by the story, some were left confused. After Harry Styles of One Direction paid his own tribute - "RIP Baroness Thatcher .x", some of his fans wanted to know who he was talking about. "i am sorry :( but who was this person?" asked one.

Mind you, his tweet was retweeted by many more than David Cameron's tribute, so he may have played a role in educating a new generation about recent history.

By late afternoon there had been more than a million mentions of the story, and the hashtag #Thatcher was trending in the UK, the US and worldwide. The company says the volume of tweets rivalled those for the announcement of the new Pope.

So how do we sum up the way Twitter has transformed coverage of a story like this? Ronald Reagan - Margaret Thatcher's political soulmate and a similarly divisive figure - died in 2004 before social media took off. Looking back at the BBC's web coverage on that death, it does include comments from readers, although they have obviously been selected by an editor some days after the event.

Now, anyone can instantly broadcast their views on Baroness Thatcher, reaching a global audience which may be moved or outraged.

So Twitter has not only accelerated the speed at which the world digests a major news story, it has democratised reaction to it. Is that a positive development? You decide - in 140 characters or fewer.

They had all come up with clever ideas to use the Raspberry Pi, the ultra-cheap computer developed in Cambridge, and they were the finalists in a competition held by the technology advisors PA Consulting.

I was one of the judges deciding who should win - and it was a tricky task.

There was the London primary school with a plan to recycle old computer components to turn the Raspberry Pi into a communications device for schools in developing countries. Their only problem - they couldn't figure out how to make Skype work on the little device,

Then there was the North Yorkshire community school which had turned the Pi into an RFID (radio-frequency identification) reader to measure lap times in their cross-country races, and the London independent school whose pupils had come up with Teacher's Pet, a way of delivering homework via USB sticks plugged into the tiny computer.

But the winners combined great teamwork with excellent use of both the Raspberry Pi hardware and inventive programming.

A team from a Cheltenham primary school came up with a system to help elderly or disabled people answer the door with a wireless keypad, using the Piface attachment for the Raspberry Pi.

Dalriada School from Ballymoney had invented a pill dispenser which allowed a GP to control what drugs a patient was taking at home. The boys and girls from the school, while wrestling with a demo which had a few teething problems, gave a compelling presentation of the need for the product and the design challenges involved in manufacturing it.

And two sixth-formers from Westminster School had the most polished and commercially attractive idea of them all, the AirPi. It combined various sensors with some clever programming to turn the Pi into an air quality and weather station.

They've even put up a site explaining how anyone could copy this idea, and building a community around the project.

If the idea behind the Raspberry Pi was to inspire a new generation to look under the bonnet of computers and get their hands dirty, these schools seemed to show it was working.

And if just a few take their ideas further and decide to start their own businesses or compete for jobs needing computer science skills, then that could make a big difference to the UK's competitiveness.

The judges did have one concern - just how few entries there had been from state schools.

One theory was that the constraints of the curriculum meant teachers were too cautious about committing the time to time-consuming projects which might not contribute directly to exam results.

Which if true, is a pity.

Mind you, it is my fault - I made her angry by adjusting a slider on a computer screen. Because Zoe is a virtual talking head created in a collaboration between Cambridge University's Engineering Department and the Toshiba Research Laboratory. Her genesis tells you something about the way business and academics are working together in the UK's leading hi-tech cluster.

There is a lot of work on virtual heads, or avatars, at the moment - you can even use Microsoft's Xbox Kinect system to create a virtual you to put in a game. But the team behind Zoe believe they have gone a step further by giving Zoe a range of human emotions expressed in her face and voice.

The face is that of Zoe Lister, the actress who played Zoe Carpenter in Channel 4's Hollyoaks, and the scientists spent some days recording her facial and vocal expressions. They then built a lightweight piece of software which allows users to input any text and then adjust to have it spoken in various moods, from happy to frightened to angry.

The project draws on expertise in speech recognition and in computer vision - ways of capturing visual data - which have been a strength of Cambridge and the Toshiba lab in particular. It has been led by Professor Roberto Cipolla, who splits his time between the Department of Engineering in the centre of Cambridge and the Toshiba laboratory on the Science Park.

Professor Cipolla says Zoe is "the interface of the future", part of a trend towards abandoning the keyboard and mouse and finding new ways of relating to computers.

To my eye, Zoe was stuck somewhere in the "uncanny valley", that no man's land between robot and realistic human replica that makes us feel uncomfortable. But she is still a work in progress, and the Toshiba/Cambridge team say they are confident that she will become far more realistic.

They are particularly proud that the program they've built is so small, making it feasible to load it easily onto a smartphone or tablet. But what is it for?

Dr Bjorn Stenger, once one of Professor Cipolla's doctoral students and now employed at the Toshiba lab, sees a number of uses: "Sending messages to your friends with your face on it," he suggests. Virtual actors or game characters are another possibility - and then there is the prospect of virtual carers or call centre employees.

There is no guarantee that "Zoe" will be commercialised, or that her inventors will profit from her. The Toshiba Lab is focussed on long-term research rather than being an incubator for start-up companies.

But what always impresses me about Cambridge is the sense that all kinds of bridges are now being built between world-class science in the university and the commercial world. The result is that some of Britain's most valuable technology businesses are continuing to emerge from Silicon Fen. That is rather a contrast with London's Tech City, which has yet to build strong links to the capital's excellent universities.

And while major international technology companies are now opening offices in East London, they are still looking to Cambridge for ideas and people. Professor Cipolla told me that one of his biggest concerns these days was that his smartest graduate students were being lured away by big money offers from the likes of Google, Facebook and Microsoft.

But some of the brightest and best are staying and building companies. As long as ideas like the digital talking head are emerging from Cambridge labs, its scientists are going to be a valuable resource for our economy.

And so by midnight, having watched the show from Radio City Music Hall with a live online audience of something over 300,000, I was able to reach the following conclusions:

The show, staged at what must have been vast expense, featured brief appearances from a couple of Samsung executives before the stage was taken over by a cast of actors. We were then treated to a mini-drama which saw the many features of the phone shown off by the compere, his family and his friends.

It's hard to describe quite how excruciating this was - imagine an under-rehearsed school play without the benefit of a friendly audience to laugh at the awful jokes.

It almost served to obscure the genuine innovations of the Galaxy S4, which Samsung's press release describes with typical restraint as "a life companion for a richer, simpler and fuller life... developed to re-define the way we live and to maximise our fulfilment of life."

It may not quite do that - but the live demo of the new translation service looked very clever, as did the standout eye-tracking feature which enables you to pause a video by simply looking away, then restart it by focusing on the screen again.

Samsung also appears to have taken gesture and voice control of the phone a stage further, and its S Health software, coupled with a series of accessories, transforms the phone into a powerful health-monitoring device, offering new competition in a growing market.

Most of these innovations, however, will be of marginal interest to most users - how often do you find you need to translate something into Mandarin on the move? And might it get a bit annoying if the video paused every time your attention wandered?

To the untrained eye, the S4 will look much like the S3 - and not radically different in its capabilities from many of the other high-end smartphones on the market, from Sony's Xperia Z to the HTC One X. Like them it is built on Google's Android platform, but last night it seemed determined to gloss over that.

There was hardly a mention of Android all evening, and I'm pretty sure the word "Google" never crossed anyone's lips. Instead the letter S predominated - S Translator, S Voice Drive, S Health - as Samsung stressed its own services.

When Android first appeared, the issue for all the brands using it was how to stand out from the crowd. Companies like HTC tried adding their own "skin", but have still ended up being seen as just another Android.

But Samsung, with a combination of huge marketing spend and the genuine excellence of its products, has won the battle to be top dog in the leading mobile operating system. Now it appears to want to go further - to make customers forget they are using an Android altogether.

Samsung and Apple have managed to make huge profits from smartphones in the last two years, while just about all their rivals have struggled to stay in the black. But the markets seem to have decided that from now on, software and services are going to be a better route to profit for both firms than hardware.

Samsung is positioning itself for that new world, where its users will live and shop in a Samsung world with their data stored on a Samsung cloud. For its rivals, and for Google, whose control of the Android ecosystem may be threatened, that is a worrying prospect.

Just as users seemed to be showing a preference for smaller tablets, Amazon is giving them a bigger one - so what does that say about where the market is heading?

Until last September it looked as though Apple, the company that created the tablet market, was pretty secure in its dominance in the UK. Sure, there were any number of Android devices, including Google's own impressive Nexus 7, but the 10in (25.4cm) iPad remained the one that most consumers aspired to own.

Then, Amazon finally brought the 7in (17.8cm) Kindle Fire to the UK, nearly a year after its US launch. With a brand name far more recognisable than the other Android contenders it was bound to do well. And the fact that it was being sold at around cost price - as Amazon boss Jeff Bezos told us last year - meant that it was the bargain tablet at Christmas.

While it is hard to get reliable statistics for tablet sales, a survey by YouGov seems to show that the Kindle Fire came from nowhere to challenge for the lead over the festive season. Its survey of people who bought tablets as gifts showed that the Fire was the single top choice, although combining the iPad and the iPad mini gave Apple a bigger share.

Overall, 2012 was the year in which tablets really went mainstream in the UK. According to Ipsos Mori, the year started with 7% of the adult population owning an iPad, with another two percent owning another kind of tablet. A year on the same company says iPad ownership is up to 16%, with 10% owning another tablet.

So the market has more than doubled, and while iPad ownership has soared, others are beginning to make inroads into its market share.

But it was the smaller tablets - the Nexus 7 and the Kindle Fire - which started to change the dynamics of the market, forcing Apple to do something that Steve Jobs had ruled out, make a smaller cheaper iPad.

With rumours that the iPad Mini is starting to cannibalise sales of its big brother, it seems somewhat strange for Amazon now to be bringing out a larger model. So will there be much demand for it here?

At £229, it is almost half the price of the full-size iPad which starts at £399. As in the US, owners will see adverts on the lock screen, unless they pay an extra £10. And the whole experience is built around driving you to Amazon content, with a home screen directing you to books and music you can buy from its store, and video from Lovefilm, the British business it bought in 2011.

The device does not feel as open and flexible as other Android tablets, nor anything like as slick as the iPad and it certainly does not have the range of apps that Apple can offer.

In fact, having spent a few days with the device, I struggle to see where it fits into Amazon's strategy. The original Kindle dominates the e-reader market, the 7in Kindle Fire is becoming the tablet of choice for more budget-conscious consumers. Will many of them pay £70 more for the same package on a bigger screen?

Still, having watched how Samsung crept up on Apple in the smartphone market, then accelerated past with a wider range of devices, maybe Amazon feels it is equipped to do the same. The good news for both firms is that the tablet revolution seems to have much further to run - the bad news for the older PC makers trying to get into this business is that they could be left trailing as Apple and Amazon race off into the distance.

Ask most people - even Londoners - what that means and I suspect you will get quizzical looks. But a Royal visit should help to put the tech cluster on the map, and perhaps make the government's ambitions to turn the area into Europe's rival to Silicon Valley look slightly less fanciful.

One Royal has already spent plenty of time visiting the area and getting involved in promoting it. Prince Andrew was supposed to accompany the Queen on today's visit, but now that her engagements have been cancelled for the rest of the week, he will be going alone.

So yesterday I went to Buckingham Palace to interview the Duke of York about the hi-tech cluster - and about his family's use of technology.

His staff had warned me that he was more "techie" than I might have expected, and that proved to be the case. Off camera, we chatted about the merits of various mobile operating systems, and what worked best in a BYOD - Bring Your Own Device - organisation which is apparently what the Palace is becoming.

Then in our interview Prince Andrew told me that the Royal family acted as "the early adoption gang", trying out new technology for the Buckingham Place IT department: "We are very fortunate, we hear about, we go and visit, we see new technology and we see new opportunities and we bring them back and go OK let's see how we can apply this. "

He said the family were enthusiastic users of Apple's iPads and all had mobile phones, though there was more caution about social networks. But he revealed that the family did use Yammer - the private social network for organisations which is among the firms he will visit today. "I've used that for seminars and forums I've held here so that people can carry on the conversation afterwards."

As for Tech City itself, the Prince stressed the importance of linking it back into the local community - something critics say is missing: "I've been working very closely with Tech City and Hackney. There is 35% unemployment in 18 to 35 year-olds in that part of London. What I want to do is to try to encourage apprentices to be taken on from the local area." There was, he said a tendency to bring in people with a university education from outside the area. "Not everybody needs a degree to work in this particular sector."

The Prince seems genuinely enthusiastic about helping to boost East London as a centre of hi-tech endeavour. He talked of businesses on the scale of Google or Amazon emerging from Tech City.

So far, however, there is more evidence of American giants like Google, Amazon and Microsoft - owners of Yammer - opening a few small offices in East London rather than home-grown businesses emerging to take them on. Tech City has the royal seal of approval and a healthy marketing budget - now it needs to show it can generate jobs and world-beating businesses.

Television Centre is now rather battered and down-at-heel, but it was once an impossibly glamorous place. My first visits were as a child in the 1960s when my mother, a production assistant in the Drama Department, brought me in for lunch in a canteen where actors in costume and other celebrities might be sitting at neighbouring tables.

I joined the television newsroom as a sub-editor in 1983, and for much of the last 30 years TV Centre - or the Fun Factory as some of the camera crews dubbed it - has been my home.

Here are a few treasures from the archive showing the rise of Television Centre and the years that followed, chosen by picture editor Phil Coomes.

Last Friday, on what may have been my last full day in my old office, I went to buy a tea round from the Filling Station, the TV Centre tea-bar immortalised on Twitter as @killingstation.

I took along a small camera, and instead of going the direct route I went via the newsroom, passing the edit suites and the N6 Studio which has been home to the main television news bulletins since the 1990s.

I edited my journey to a soundtrack of clips from old news programmes that have come from Television Centre. It is my little tribute to the place which has played such a big part in the history of broadcasting in the UK.