Deputy PM and Lib Dem leader Nick Clegg, who also went to see the Queen today, argues that the "last thing" the country needs is to be pulled left or right by Labour or the Conservatives. UKIP leader Nigel Farage outlined five key pledges from his party and said there was time for an in/out referendum on the EU to be held this year. SNP leader Nicola Sturgeon called this "a social justice election" and demanded an end to austerity, as did Plaid Cymru's Rhun ap Iorwerth, who foresaw a "great opportunity" for Wales if his party held the balance of power. And actor Martin Freeman became the first celebrity to endorse a party in the campaign, appearing in a new Labour election broadcast.

Plaid Cymru's Rhun ap Iorwerth tells the BBC that there would be "a great opportunity" for Wales if Plaid held the balance of power. "The stronger Plaid Cymru is, the stronger Wales will be in any talks on deals following May 7," he says. The Welsh Assembly Member describes his party's years of coalition with Labour in Cardiff from 2007-11 as "some of the most progressive years since devolution". The "austerity experiment" has failed and it is time to try something new, he adds.

It is time for us to hand over to our colleagues, Angela Harrison and Tom Moseley, for continuing live coverage of the first official day of the election campaign. Parliament has dissolved and there are no longer any MPs until the results are declared after 7 May. Following an audience with the Queen, David Cameron said the Conservatives had "turned the country around" and urged voters to let him finish the job. Labour leader Ed Miliband launched his party's business manifesto and warned of the consequences of an EU referendum for the UK economy.

Bookmakers William Hill say someone has staked the first five-figure sum on the political make-up of the next government. A gambler in Wiltshire has put £10,000 on the Tories to win an overall majority at odds of 11/2. He would win £55,000 if the Conservatives won outright.

The bookie has cuts the odds on a Conservative majority government to 9/2 - making it third favourite, after a Labour-led minority administration (2/1) or a Tory-led one (3/1).

Scottish Conservative leader Ruth Davidson has said she would prefer to see the Tories rule as a minority government rather than enter into another coalition. Ms Davidson said a Conservative majority at the general election "doesn't look likely right now" as she launched her party's campaign in Edinburgh. She pointed to the example of the SNP minority government at Holyrood from 2007-11. "I think I would prefer a minority government, and we've seen in Scotland how that can work," she said. However, she added that the Conservatives would continue to work for an overall majority.

In Belfast, Sinn Fein president Gerry Adams said his party was "totally and absolutely opposed to austerity north and south" - while the parties at Westminster were committed to further austerity. Launching a "people's pact" at Belfast Castle, Mr Adams said: "Any parties which contemplate endorsing or supporting a cabinet of millionaires who are behind budget cuts, cuts to public services and cuts to social protections are ignoring the needs of the people in favour of narrow self-interest."

More pageantry as the royal proclamation for the election of a new Parliament is read out in Edinburgh, marking the official start of the election campaign.

Conservative chairman Grant Shapps has conceded the party's claim that Labour would raise taxes for working families by £3,028 is a "guess". He said the Conservatives need to "have to have a way of explaining how the Labour plans would affect this country" and the number is based on previous statements by Labour figures. "Unless they're doing to tell us exactly how they're going to do it, then I'm afraid we're left having to guess," he said.

Investment manager Gina Miller tells BBC News she is "more than happy" to be quoted in the Labour Financial Times ad. "This is all getting a bit silly," she says. "I was consulted, I saw the quote that was going to go in and I was more than happy for it to be included in the advert. I happen to be a Labour supporter but this was about business leaving Europe and whether it was a good thing." Staying in the EU means "stability", she adds.

Reality Check

It turns out that the figures the Conservatives are using for working households also include so-called “mixed” households (in which at least one adult is employed and at least one is not), which means there are 17 million of them. That means a tax rise of £3,028 for each of them would raise more than £50bn. But thanks to the Institute for Fiscal Studies, which has explained that the figure, external is reached by adding up all the annual tax rises the Conservatives predict that Labour would have to make by 2020, a method it describes as “at best, unhelpful”. But the IFS also estimates that the total amount of extra money that Labour would need would be £6bn, not £30bn anyway.

Image source, Reuters

Nigel Farage thinks UKIP is going into this election campaign with both money and momentum. The party is polling in the low double figures, which is the best it could have hoped for. It has unveiled a raft of new policies in an attempt to broaden its appeal, but an EU exit and immigration remain high priorities. Another priority is to get Mr Farage elected to Parliament.

As an American political reporter I find all the pageantry surrounding the start of the general election quite exciting. In 1996, US President Bill Clinton didn't even bother to formally announce he was running for re-election.

Image source, AP

Speaking in Westminister a moment ago - and unveiling UKIP's five pledges to voters - Nigel Farage says UKIP offers a "completely distinctive plan from the other political parties." He says UKIP is the only party saying the UK should have a trade association with Europe rather than membership of the EU. Because it favours EU withdrawal, UKIP is also the only party with "a solution to the immigration crisis", he argues. And he says UKIP would spend £3bn extra on the NHS using money saved from annual EU contributions.

Image source, Labour

An early celebrity endorsement. Actor Martin Freeman - aka Dr Watson and Bilbo Baggins - gives his support for Labour in a new party broadcast, external. In it, he says the election is "a choice between two completely different sets of values". He says Labour's values are those of "community, compassion, fairness - I think, all the best things about this country". He also claims that "it seems that the Tories don't really believe in the NHS" and have "sod all to offer the young", in a film which also features the voice of fellow Labour supporter David Tennant.

tweets:, external New #ge2015, external poster from @UKIP, external (not unveiled yet)

tweets:, external At UKIP launch, they are outside Home of EU parl in London, numbers of snappers they could only have dreamt of 5 yrs ago

Liberal Democrat Simon Hughes says his party has "played our part" in delivering one of the highest rates of growth in Europe. "Nobody's pretending that people are having an easy time," he says, "but we've pulled the economy back from the brink and we're proud of that." He says the Lib Dems in coalition have been able to stop the Conservatives "doing extreme things that we thought were bad for the country". He also claims that his party's record on tuition fees "comes up rarely" on the doorstep now.

Image source, Getty

Oh dear, looks like there might be trouble with Labour's gold bus before it even gets going. Insert "wheels have come off/campaign stalled/etc" joke here...

Image source, PA

Not quite kissing a baby but almost hugging one... Nicola Sturgeon has also been campaigning in Glasgow this morning. As Gordon Brown promised - just across town in fact - that this was "a social justice election", the SNP leader told another audience: "We can achieve an end to the austerity cuts - implemented by the Tories and backed by Labour - which are causing so much damage in our communities and holding our economy back."

Norman Smith
Assistant political editor

The battle lines are drawn. The Conservatives will focus remorselessly on the economy and leadership, while Labour want to concentrate on the NHS and the cost of living. The Lib Dems, meanwhile, are promising to cut less that the Conservatives and borrow less than Labour. UKIP have been focusing on immigration and proposing to introduce an Australian-style points system.