Inside Story: Politics, Intrigue and Treachery from Thatcher to Brexit. Philip Webster

Cameron’s aides and supporters believed that he had no choice and that the time to settle the issue had come. One told me after 23 June: ‘There really was little alternative. The political pressure was unstoppable.’

      But it has to be said that Cameron called the referendum for party political reasons and not for the national interest. There was no clamour for it in the country and the decision was to blow up in his face and put the country on a deeply uncertain path.

      I believe the referendum was a mistake. Cameron could not be sure of winning, and he lost. Thatcher once said that referendums ‘sacrificed parliamentary sovereignty to political expediency’ and most leaders hate them because voters do not necessarily use them to decide the issue in question but to make a protest. In this referendum, ‘Leave’ voters did so for all kinds of reasons. ‘Remain’ voters just voted to remain.

      By the time he capitulated to the Right, Cameron had often been called the ‘essay-crisis’ PM, the leader who only turned his attention to problems at the last moment and then rushed through an answer to them. The referendum pledge helped him see off his own right wing and the threat of UKIP, and may well have helped him win outright in 2015. But the country was landed with a critical decision on its future and millions felt ill-equipped to make it.

      Cameron’s second-biggest error was overconfidence. As recently as December 2015 he told his European colleagues that he was a winner and they should not worry too much. His serendipity may have led to him accepting a deal from Brussels that was not good enough, and once the campaign was under way he did not use all the weapons available to him, as I will explain.

      In March 2016, Cameron’s campaign was abruptly thrown off course by an event that he should have anticipated but did not. Two days after the 2016 Budget, Iain Duncan Smith, the work and pensions secretary, resigned. The immediate issue was cuts to disability benefits. The reason was George Osborne.

      Osborne and the man in charge of the biggest government budget did not get on. IDS had row after row with the chancellor over his repeated attempts to cut benefits for working people as his main weapon to tackle the deficit. I understand the resignation had been brewing since January 2014, when Osborne announced he would make a further £12 billion of cuts in welfare in the next parliament. He had not discussed the plan with IDS. ‘It was a bounce,’ he has since told friends.

      We know that Osborne did not have a high opinion of his colleague. As Matthew D’Ancona told us in his book In It Together: ‘“He opposes every cut,” Osborne complained to one friend.’ Nor was he confident that IDS had the IQ. ‘You see Iain giving presentations,’ he confided in allies, ‘and realize he’s just not clever enough.’ IDS, I learnt, has no higher opinion of the ex-chancellor. A friend said: ‘Iain regards George as arrogant. He is not collegiate. He lands the government in one shambles after another by his refusal to consult. He fancies himself as the master strategist. His record does not justify such pride.’ Another friend said: ‘Iain does not like George or his cronies. He encroaches on everyone’s pitch. He is mad for a headline – so in the 2016 Budget we got his great announcement that all schools would have to become academies. Then six weeks later poor old Nicky Morgan [former education secretary] had to retreat. It is one omnishambles after another.’

      That was a reference to Osborne’s 2012 Budget when what seemed like a decent package on the day collapsed quickly with retreat after retreat on matters such as taxes on Cornish pasties and caravans. It became known as the ‘Omnishambles Budget’.

      But when, on the early evening of 18 March 2016, Downing Street received a letter from IDS resigning over the disability cuts, a shocked Cameron realized this was deadly dangerous to him. He called IDS, asking him to hold off until they had spoken face to face. Soon government sources were briefing that the £1.3 billion cuts were being ‘reviewed’.

      But IDS had had enough, and in a second telephone call told Cameron his mind was made up. During furious exchanges, Cameron was reported to have called IDS a ‘shit’, something that neither side has seen fit to deny. Duncan Smith’s friends maintain he had been surprised by Osborne’s decision to put the cuts in the Budget so that they could be counted as billions of savings in the deficit battle, but that the last straw was to put them in the same package as tax cuts for the better off. ‘It went against Iain’s whole social justice message, and he had to go,’ an insider said.

      IDS had been in constant rows with Osborne over the previous six months about the chancellor’s plan to cut tax credits for three million people, eventually defeated by the Lords and dropped, and the IDS plan to merge several benefits into a universal credit. One friend said: ‘Iain regrets not going earlier. He thought about resigning before Christmas 2015 and wishes he had. He tried to defend the Budget but lost heart and realized he could not in all honesty do so.’

      IDS, for decades an opponent of the European Union, has insisted since that his resignation had nothing to do with Europe, and he stayed out of the campaign for a few weeks to show that. But his enemies maintained that the whole exercise was designed to damage Cameron and Osborne at a time when they could least afford it. Some claimed that IDS had planned to quit the Government dramatically during the Budget debate, something his friends have denied.

      I can confirm, however, that he was one of several ministers who called on Cameron privately earlier in the year to allow ministers freedom to speak out during the referendum campaign. IDS told him that if he did not grant the concession, ministers would resign and that would be far more damaging to the Government. I understand that the key figure in persuading the PM to give way – much to the unease of key pro-Europeans like Michael Heseltine – was Chris Grayling, leader of the House of Commons.

      By the end of 2015, Grayling had concluded that the deal the Prime Minister had been negotiating with Europe would not be good enough to change his view that Britain would be better off out. He decided that he would campaign to leave but delayed until the New Year before telling Cameron. After the regular 8.30 a.m. meeting of ministers, aides and Commons business managers on Monday, 5 January, Grayling stayed on for a private chat with the PM. He told him that he intended to campaign for an ‘Out’ vote and offered to resign. On the same day, Theresa Villiers, the Northern Ireland secretary, had a similar conversation.

      Cameron had been moving towards allowing ministerial freedom as Harold Wilson had for Labour ministers in the 1975 referendum but he had not intended to announce it at this stage. While Grayling’s remarks were an offer to resign, Cameron would have seen them as a threat, and concluded that ministerial resignations would be more damaging than allowing them latitude. He may have concluded that keeping them inside the tent would avoid the more abrasive campaigning that would be inevitable if they were speaking from outside the Cabinet. He got that wrong. He was to be shocked by the interventions of Outers such as Gove, Johnson, Leadsom and others.

      So why in the end did Cameron lose a campaign that he believed from 2013 that he would win and win well?

      As they gathered on the morning before referendum day there was cautious confidence – much more than there had been for some time – among the leaders of ‘Britain Stronger In Europe’, the official all-party campaign to remain in the EU.

      Andrew Cooper (Lord Cooper of Windrush), the founder of the polling company Populus and director of strategy for David Cameron between 2011 and 2013, had for a few days been bringing better news to the gathering of Downing Street aides (including Craig Oliver, the communications chief) and Labour and Lib Dem strategists. Less than twenty-four hours before the polls opened the PM was told that he would win by several points.

      But the late confidence was misplaced because Downing Street and other campaigners had underestimated the impact of immigration on the campaign and overestimated the impact of the economy. The Tories had won the 2015 election on the back of economic competence and thought they could do it again. There appears to have been a basic mistake in the so-called ‘playbook’ on which the campaign was based.

      The previous summer, on the basis of a survey involving thousands of respondents, Populus presented the board of ‘Stronger In’ with a finding that suggested that the economy was massively more important than immigration to most voters. The conclusion was not challenged and treated as