As voters across the country headed to polling stations, a small group of academics met amid high secrecy in a windowless room at a BBC building in central London. Even now, no one is allowed to know precisely where the office was or what went on inside it. Led by John Curtice, one of the country’s leading psephologists, the team included Steve Fisher from the University of Oxford and Robert Ford, senior lecturer in politics at the University of Manchester. From early morning, exit poll data, compiled at 140 polling stations, poured in. Unlike every opinion poll published in preceding days, all of which showed the country heading for another hung parliament, this was the record of where voters had actually placed their crosses in the secrecy of the polling booths.  By early afternoon clear patterns were emerging, allowing the academics and number crunchers to make detailed seat predictions nationwide. Curtice’s team knew the data was extraordinary and that they were sitting on dynamite. If the results of this huge 20,000-plus sample were accurate indicators of the national result, the country was heading for the biggest election shock since Churchill’s defeat in 1945 – one that would have momentous implications for British politics and possibly the future unity of the UK. It would blow every prediction about general election 2015 out of the water.  As Big Ben struck 10pm and polling stations closed, staff at Labour’s London headquarters awaited the moment of truth. The results of the Curtice exit poll flashed up on the BBC, Sky and ITV. “I looked round and saw rows of people all with their hands over their mouths,” said a Labour staffer. “It was if the whole room was witnessing some terrible tragedy unfold before their eyes.”  The blue box for the Tories showed they were heading for 316 seats. Not even the worst Labour scenario had put them that high. Labour was projected to win just 239, a catastrophic tally that would give Ed Miliband no chance of forming the next government. The Lib Dems would take only 10 seats, a disaster for Nick Clegg. At the Shoreditch Ace hotel in east London, the New Statesman was holding its election night party. Messages flashed up on mobile phones. Other than a fist punch from one Tory-supporting woman in the corner of the room, people froze in shock mixed with incomprehension. A text received by a Daily Mail journalist read: “News-desk just erupted in cheers”.  Miliband was at home in his Doncaster constituency with his wife, Justine, and a team of close aides, including Stewart Wood and Bob Roberts. David Cameron was holed up in his Witney constituency with his small team. As they all tried to digest the figures, Miliband’s aides made contact with London HQ and agreed to put out a line pouring cold water on the poll. A “Labour source” texted a statement to journalists: “We are sceptical of the BBC poll. It looks wrong to us.” Cameron’s team erupted with relief and joy, but the Tories knew they had to be cautious. Readjusting expectations, and adjusting emotions, so quickly was impossible. In the BBC studios Paddy Ashdown, who had masterminded the Lib Dem campaign, told David Dimbleby that if the exit poll was correct “I will publicly eat my hat on your programme”. Clegg and Ashdown had insisted that their party would do far better than the pundits had predicted and polls had suggested. The Lib Dems expected around 30 seats, not 10. No one could take this in.  Some 14 hours later, the full extent of the political earthquake that unfolded overnight was laid bare. Three party leaders – Ed Miliband, Nick Clegg and Nigel Farage – had resigned in the space of under an hour. British politics was transforming at a dizzying speed. Cameron had been to see the Queen and said he could form a government, not simply as the head of the largest party but with a working majority of 12. He said that this election success was the “sweetest” he had ever experienced.  The Tories had done better than even the Curtice exit poll had suggested, returning 331 MPs to the Commons when few had thought they would pass 290. Labour’s total had fallen to only 232, comparable with the dismal election nights of the 1980s. Scotland had returned 56 SNP MPs out of 59, as Labour was obliterated by a nationalist onslaught north of the border. The Lib Dems had been reduced from 56 MPs to eight. Farage had fallen short in Thanet South, as his party failed to break through, losing one of its two seats, on a night of massive disappointment .  Labour’s night of gloom had no respite: disaster followed disaster. After predictable early results in safe Labour seats in north-east England, evidence piled up that the Tories were outperforming in key marginals in the north-west, the Midlands and the south. These were seats Miliband had to win to have any chance of forming the next government.  At 1.50am the Tories comfortably held the key battleground of Nuneaton, and Miliband and his team knew the game was more or less up. The swing was not to Labour but to the Tories. Miliband’s mind turned to resignation and he and his team packed up to return by car to London. Shortly after 2am, the extent of the SNP landslide in Scotland, which would see Labour lose all but one of its seats there, became clear. The party’s campaign chief Douglas Alexander lost Paisley and Renfrewshire South on a massive 34% swing to the SNP, toppled by a 20-year-old student, Mhairi Black. Jim Murphy, leader of Scottish Labour, would suffer a similar fate in Renfrewshire East.  David Blunkett spoke of a “tsunami” that had torn across Scotland as the SNP took all but one of Labour’s 41 seats. For the Lib Dems it was carnage the length and breadth of the UK. After they lost their southern stronghold of Eastleigh to the Tories, and before the biggest of their names fell – Danny Alexander, David Laws, Simon Hughes, Ed Davey and Vince Cable – Ashdown headed for the National Liberal Club in Whitehall Place hoping to find some comfort among friends. He made a short speech and asked the 200 gloomy Lib Dems there to raise three cheers for Nick Clegg. There were boos from some and cries of “let the guilty men retire” rang out from the back of the hall. The recriminations had begun.  In Labour, Lib Dem, and to a lesser extent Ukip, circles, the same simple questions were being posed. How could they all have got it so wrong, and how and why did the polls mislead them? Even Tories watched the election unfold in states of utter disbelief. Paul Goodman, the former Tory MP, now editor of ConservativeHome website, said he had been unable to comprehend what was happening. “It was the most extraordinary election I have ever known. The results suggest it may have been the primal fear in voters’ minds of Miliband governing with the Scots, coupled with fear of what he would do to the economy. It seems that [David Cameron’s election guru] Lynton Crosby’s campaign worked. But why the polls didn’t pick this up is a mystery.”  Tessa Jowell told David Dimbleby that she simply could not reconcile what was happening on the night with her experiences on doorsteps. “I am a pretty experienced campaigner,” she said, mystified by it all.  At around 9.30am Miliband and his team arrived back in London. The Labour leader, who had believed hours earlier that he could be prime minister by the morning, and his wife, Justine Thornton, entered Labour HQ. There was silence in a room packed with 200 people. They were watching the former shadow chancellor, Ed Balls, who had just lost his Morley and Outwood seat after a recount, give his resignation speech. Thornton and many others were in tears. When Balls ended, they stood up and applauded.  As Labour, the Lib Dems and Ukip now prepare for leadership elections, and Cameron puts together his new government and plans the Queen’s speech for 27 May, postmortem examinations are under way.  Miliband’s team believe that many voters south of the border were simply frightened away. Relentless Tory “lies” claiming a Miliband government would not only wreck the economy but would be in the pocket of the SNP had paid off spectacularly. The “soft” element of the Labour vote – those who liked Miliband but were not entirely convinced – was susceptible, the former leader’s inner circle now thinks, to the fears that Crosby’s campaign instilled in them. They also believe that many people were embarrassed to tell pollsters that they were going to vote Tory. “They were bullied by the Tories but they could not admit it,” said a source close to Miliband. “We believed we were doing well, because we could not see this going on. The Tories’ tactic worked.”  Ukip voters returned to the Tories more than they did to Labour. Murphy said that north and south of the border Labour was caught in a perfect storm. “We were hit by two nationalisms,” he said. “A Scottish nationalism reassuring people that they could vote SNP and get Labour. And an English nationalism stoked up by Cameron: warning vote Labour and get SNP.”  The Lib Dems seem to have been swept away by similar forces as voters bought into the Tory message that it was a choice between the chaos of Labour with the SNP or stability with the Tories. Labour officials concede that maybe they should have tried to play as hard and as rough as the Tories did, but simply weren’t able. “We tried negative campaigning in the last two weeks over benefit cuts and the NHS, but we were not very good at it. Our heart wasn’t really in it.”  As leadership contenders prepare to throw their hats into the ring for Labour and the Lib Dems, the debates in both parties will focus on how to move forward from defeat. Tony Blair wastes no time in joining the discussion, insisting in the Observer that the party will never win unless it is on the centre ground.  Bitter battles between the Blairite wing of the party and the Milibandite centre-left are already breaking out. Former home secretary Alan Johnson said that the party needed to have a “proper rethink” to resolve “deep problems” in what he described as a 10-year mission. Miliband, he suggested, had failed to connect with people who wanted to get on in life. “The issue of aspiration in people’s lives – we can no longer relate to them as a party of aspiration,” he said. “It’s an incredible thing now that I was part of a successful government that did really good things, but you’d think that Tony Blair had lost us three elections, not won us three elections. It’s almost de rigueur now not to mention his name.”  On Friday, a likely contender for the leadership, Andy Burnham, had argued that Labour was too much a party of the south, which ignored the interests of other parts of the country at its peril. No one has yet dared to set out ideas for how Labour rebuilds in Scotland, without which the task of ending the Tory run in power could be hopeless.  As the Conservatives cruised past the magic number of 323 MPs at lunchtime on Friday – the number needed for the working majority that few had believed they would ever get – there was a notable absence of triumphalism among their ranks. The party had been preparing for recriminations about its failure to win a majority – not success on anything like this scale. But the main reason for the party’s sober response was that the challenges facing Cameron, with a majority smaller than John Major’s in 1992, are huge: the future of the UK and its place in Europe is now at stake.  Cameron presides over a deeply divided UK, in which 56 of the 59 Scottish MPs at Westminster belong to a party whose mission is separation from Westminster.  Unsurprisingly, SNP leader Nicola Sturgeon is insisting that there can be no more “business as usual”. The prime minister moved fast on Friday morning to promise Scotland a far-reaching devolution settlement that would match any comparable arrangement anywhere in the world. But he will need to deliver on his promises, and more.  His second term is fraught with risk. He is set upon a course of spending cuts to balance the nation’s books which will be unpopular enough south of the border, but which is the very opposite of the anti-austerity message which helped carry the SNP to its landslide in Scotland.  Cameron is also about to embark on an in/out referendum on the UK’s European Union membership. Many Tory MPs want to leave the EU. But the SNP is committed to staying in. A no vote could thus lead not only to a momentous break with Europe, but also to the breakup of the UK.  Cameron secured his second term on a night of unbelievable shock and drama. But given the gravity of what will be at stake during the next five years, that 12-seat majority – so longed-for and so unexpected – will soon begin to look wafer-thin.
It was a night of political drama that changed the course of British politics. Labour and the Lib Dems have been left leaderless, the SNP are overjoyed and David Cameron must manage a slim majority many thought unobtainable