The Tories outperformed even their own expectations by winning a majority of seats, while Labour and the Liberal Democrats suffered bitter losses. Meanwhile, Scotland has been seized by the nationalists.

Labour's Ed Miliband, Liberal Democrat Nick Clegg and UKIP's Nigel Farage have all resigned as party leaders – though Mr Farage foreshadowed a possible return in September.

Mr Cameron echoed Paul Keating in celebrating his unexpected success as "the sweetest victory of all".

Mr Cameron told supporters at Tory HQ: "I'm not an old man but I remember casting a vote in '87 and that was a great victory. I remember working in '92 and that was an amazing victory. And I remember 2010, achieving that dream of getting Labour out and getting the Tories back in and that was amazing.

"But I think this is the sweetest victory of all.

"The pundits got it wrong and the pollsters got it wrong," he said. "I never quite believed we'd get to the end of this campaign in the place we are now."

After midday on Friday in Britain, 14 hours after polls closed, the final results came in that gave the Conservatives government in their own right.

The narrow majority slams the door on pre-election speculation about a new era of multi-party politics, in which only coalitions could rule Britain.

The Tories gained seats mainly by eviscerating their former coalition partner, the Liberal Democrats, who lost several senior MPs and now face an existential crisis and a near-certain change of leadership.

In his resignation speech, Mr Clegg said the results were "immeasurably more crushing and unkind that I ever feared".

"Liberalism is not faring well against the politics of fear."

A senior Liberal Democrat minister, Business Secretary Vince Cable, lost his seat to the Conservatives.

Labour failed to win most of its target seats, and was stunned by a surge of support for the Scottish National Party. It was the party's worst performance since 1987.

An ashen-faced Ed Miliband, speaking after retaining his own seat, said it had "clearly been a very disappointing and difficult night for the Labour Party. In Scotland we have seen a surge of nationalism overwhelm our party."

He said he was "very sorry" for the losses in Scotland, and the next government had a "huge responsibility in facing the difficult task of keeping our country together".

Later, in London, he resigned as Labour leader, saying the party must rebuild but "we have come back before and this party will come back again". But the party will not be able to call on shadow chancellor Ed Balls, who lost his own seat by a few hundred votes.

"The personal disappointment I have at this result is as nothing compared to the sense of sorrow I have at the result Labour has achieved across the UK," an emotional Mr Balls said after the result was declared.

The Scottish National Party grew from 6 to at least 56 of Scotland's 59 MPs in Westminster - leaving the Union politically fractured, and threatening a renewed push for the northern nation's independence.

One seat in particular told the story of the night. In Scotland, the man in charge of his party's campaign, Labour shadow foreign secretary Douglas Alexander, was defeated by a 20-year-old student for the SNP. Mhairi Black will reportedly be the youngest MP to sit in the House of Commons since 1667.  She was only two when Tony Blair won power in 1997. In the same seat, the Liberal Democrats received their lowest number of votes in any seat since 1859.

Liberal Democrat Chief Secretary to the Treasury Danny Alexander and Scottish Labour leader Jim Murphy also lost their seats to the SNP.

"The Scottish lion has roared," the SNP's Alex Salmond said after winning his own seat of Gordon from the Liberal Democrats. He called the result in Scotland an "extraordinary statement of intent" that no government would be able to ignore.

SNP leader Nicola Sturgeon said Labour could not blame the SNP "for not being strong enough to beat the Conservatives", depriving the country of her hoped-for progressive alliance.

Another of the night's big losers - in terms of seats - was Nigel Farage's UK Independence Party. Despite gathering 3.8 million votes, more than twice that of the SNP and one and a half million more than the Liberal Democrats, UKIP could claim only one seat.

UKIP leader Nigel Farage said "the system is bust and there will be a great demand for it to change".

He also announced his resignation, though he said he may stand again for the position in September.

On Friday morning Mr Cameron said there had been "a positive response to a positive campaign" and now his government would have a chance to build on the foundation laid in the last five years. In a nod to the political change in Scotland, he said his aim was "to govern for everyone in the United Kingdom".

Pre-election polls had predicted a tight race. However exit polls, and early results, suggested either a big failure in polling methodology, or a change of heart at the last minute as British electors stood in the polling booths.

The election result could trigger years of uncertainty over Britain's position in Europe and the world - and its own identity.

Mr Cameron will be under pressure to deliver on his promise for a referendum on Britain's membership of the European Union, as early as next year.

But a vote to leave the EU would likely trigger a new referendum In Scotland, one the nationalists would be in a very strong position to win.

Even if Britain votes to stay in the EU, a Scottish electorate so significantly at odds with the rest of the country could increase calls for a new independence referendum.

There were indications on Friday that Mr Cameron would have to quickly make a "significant gesture" towards Scotland in order to keep the peace.

Newly-elected MP Boris Johnson, a possible future Tory leader, predicted "some kind of federal offer".

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