Image source, AFP

The front-runner for the French presidency has said he would not punish the UK for backing Brexit if he wins power. 

Emmanuel Macron made the comments as he welcomed London mayor Sadiq Khan to his campaign headquarters in Paris. 

Mr Macron said: "The question is not to punish the UK for a vote made by British people. My priority will be to protect the European Union, the interests of the European Union, and the interests of European citizens. 

"And my deep wish is to have Great Britain with the European Union in another relationship. I think especially on defence matters it's important to work together."    

The Mayor of London wants the Prime Minister give a 'cast iron' guarantee to EU citizens in London.

Sadiq Khan says many Europeans have made London their home and they now face an uncertain future. 

It comes on the day that Theresa May invokes Article 50, the formal notification that begins UK's departure from the European Union.

How Article 50 presents an opportunity and a challenge for Nicola Sturgeon.

The Conservative MP for Dover, Brexit-supporting Charlie Elphicke, is happy with today's front page of The Sun

Former UKIP leader Nigel Farage is in an upbeat mood, telling the BBC that he "couldn't be happier".

The delivery of the Article 50 letter marks the "point of no return" for the UK's membership of the EU, he says.

Although there will be plenty of arguments over the next two years, he says the main thing is the UK will be an "independent, self-governing nation" by 2019.

Image source, EPA

Theresa May has left Downing Street to make the short journey to the House of Commons, where she will take Prime Minister's Questions at midday and then make her historic statement about Brexit. 

England's oldest man has said he is a "bit irked" to be celebrating his 109th birthday on the same day Article 50 is triggered.

Bob Weighton, from Alton, Hampshire, said he was "not enamoured" with all of the European Union's decisions and spending, but felt quitting was a "mistake".

He said Theresa May signing the letter was "[not] a step forward at all", adding: "She didn't ring me up to see what my reaction would be!"

Read more from Bob here . 

BBC Radio 5 live

Image source, Reuters

London Mayor Sadiq Khan has told BBC Radio 5 live's Emma Barnett that if London "suffers and struggles" after Brexit, the rest of the country will "suffer" as well. 

The Labour politician said although it was important to respect the referendum, as opposition party, Labour should "not be afraid to hold [the government] to account" if it didn't get the best possible Brexit deal."It's crucial the government recognises that if this process ends badly, it could lead to fewer jobs in London, less growth, less prosperity. That's bad for the UK and it could be bad for the EU too", he said.

Mr Khan added that it was in European leaders' interests to give Britain a good deal, as corporations that left London may not choose to relocate to Europe.

"They should not assume that any businesses that leave London will go to Paris, Madrid, Frankfurt, Berlin Brussels... The more likelihood is they'll go to New York or Singapore and Hong Kong." 

"A hard Brexit punishing the UK does not benefit the rest of Europe. We will end up losing."

BBC News Channel

Former Lib Dem leader Nick Clegg, who is now the party's EU spokesman, says senior Brexiteers in the cabinet and elsewhere in politics now need to be held to account for the promises they made during the referendum campaign 

Image source, PA

The BBC's Europe correspondent Kevin Connolly has been working with the BBC's Reality Check team and the PM programme to answer your questions about what triggering Article 50 means.

What happens once Article 50 has been triggered?

Firstly, and most obviously, is that two years to the day of that triggering statement from Prime Minister Theresa May, the UK will formally cease to be a member of the EU.

However, Article 50 says the negotiations can be extended beyond the two-year period if all countries unanimously agree they want more time.

But it is in both sides' interests to have a speedy divorce within that two-year timeframe.

During this period there will be toing and froing between the European Commission in Brussels and the member states whilst they sort out negotiating positions. Then the talks will commence.

Read more  about what will happen to EU residents in the UK and Britons on the continent and what Theresa May's red lines are in the negotiations.

Image source, Reuters

This is not directly related to what is going on in Brussels today but is likely to be a talking point both in the City of London and among MPs. 

EU regulators have blocked London Stock Exchange's £21bn merger with German stock exchange Deutsche Boerse.

The  European Commission said, external  the deal would have created a "de facto monopoly" for certain financial services.

The merger would have combined Europe's two largest stock exchange operators.

London Stock Exchange Group warned last month that the deal was unlikely to receive EU approval over concerns it would limit competition.

Not everyone is happy with today's developments, of course, and supporters of the Open Britain group are out in force in Westminster to make their feelings known.

Image source, AFP

Image source, AFP

It isn't just Nicola Sturgeon and the SNP looking at a more independent future as a consequence of Brexit. 

The triggering of Article 50 could also see the start of "Wales's renaissance as an independent European nation", according to one MEP. 

Jill Evans of Plaid Cymru said the UK government was "preparing to crash out of the EU" without thinking about the consequences for Wales.

"I will leave no stone unturned in finding the best opportunities for Wales out of the turmoil that lies ahead of us," she said. 

"I will take any and every chance to influence the negotiations to keep us in the Single Market and to have the ability to continue participating in the many EU programmes that have benefitted Wales.

“We have not achieved our full potential and today must mark the start of a search for alternative ways of doing that."

Image source, PA

Here are some thoughts from the BBC's business editor Simon Jack about what lies in store for British businesses after Brexit. 

The number one business concern is failure to agree a trade deal on preferential terms with the UK's largest market for goods and services. The limit of two years is seen by most companies as either pretty tight or impossible.

Failure to get it done may mean extra costs and red tape that would make UK companies uncompetitive. Some sectors are more vulnerable than others.

The UK car industry is connected to a Europe-wide supply chain that sees components travel to and from the EU several times and be delivered just in time for assembly. Tariffs and border hold-ups could seriously hamper that process.

The European financial services industry is concentrated in London.UK and international firms based there can sell their services across the EU. That could become more difficult after Brexit.

Both examples illustrate why many have called for a transitional period to either give extra time for negotiation or to get used to any new arrangements.

The government has signalled willingness to consider this, but has also said it is prepared to walk away from negotiations if it doesn't get the deal it wants.

Business groups such as the CBI have warned against favouring some sectors over others in the negotiation, but the government has already shown it is prepared to go to considerable lengths to reassure carmakers such as Nissan.

Read more

The Royal Institution of Chartered Surveyors says unless the free movement of skilled labour is secured during negotiations to leave the EU, industry in the UK will be "under threat". 

According to the organisation, 8% of the UK’s construction workers are EU nationals.

Jeremy Blackburn, RICS' head of UK policy, said a loss of access to the European labour market has "the potential to slowly bring some of the UK’s biggest infrastructure projects to a standstill," including new airports and high-speed rail. 

But he also called for more to be done by industry to ensure a stronger skills base in the UK. 

“Britain must retain its front line position on the international stage," added Mr Blackburn. "However, it is unrealistic to expect government to deliver a successful Brexit without the full – if sometimes constructive – support of industry."

There are quite a few Conservative MPs and peers who backed Brexit who are understandably in a joyous mood today. Here's a selection of what they are saying on social media.

The business group, the CBI, is calling for certainty for EU citizens working in the UK, and British citizens working on the continent, as an "early win" to reassure businesses about a successful Brexit. 

The organisation's deputy director general, Josh Hardie, also called for discussions on new trade deals to go "hand-in-hand" with negotiating the UK’s exit and for both sides to commit to interim arrangements if a deal is not possible within the two year time frame as ways to allay business fears about the future outside the EU. 

"It’s in everyone’s interests to get the best deal," he said. 

"Above all, UK companies need to know as soon as possible about the UK’s future trading relationships. That’s why the next six months are crucial."

Daily Politics will be on air for an extra half hour today to bring you all the drama of the Article 50 letter and Theresa May's statement.

Before that, we have got Prime Minister's Questions as usual at midday. The two-hour show starts at 11:30 BST.