How does an idea banished to the tundra of irrelevance make its way back to the mainstream? First, a moment of recognition - and ignition - is required. Someone must dare to make the initial leap, to retrieve the frozen thesis from its glacial prison.
In the case of Brexit, it was Norman Lamont, the former chancellor of the exchequer, who dragged the idea back from the snowy wastes. Since the 1975 referendum on Common Market membership - in which British voters opted to stay in by 67% to 33% - the notion that Britain might be better off outside the European Community had lost traction, apart from on the political fringes. Yes, withdrawal remained official Labour policy for much of the 1980s; but this was one of many reasons why the party was still unelectable.
So Lamont's decision to grant the idea mainstream credibility was a significant moment - more so even than it seemed at the time. Most of the memoirs and histories cite his speech at a fringe meeting at the 1994 Conservative conference in Bournemouth, in which he railed against the tide of EU integration: "One day it may mean contemplating withdrawal. It has recently been said that the option of leaving the Community was 'unthinkable'. I believe this attitude is rather simplistic."
For a senior politician, recently sacked as chancellor, to make such a statement was an occasion of high drama. But it was not the first time that Lamont had road-tested the idea. I was present earlier that year at a private meeting of the Conservative Philosophy Group, at which Lamont had urged his audience - fellow politicians, academics, journalists - to bring Brexit (as it was not yet known) down from the naughty step of political discourse and restore it to the range of serious possibilities available to governments.
The meetings of the group, in Jonathan Aitken's house in Lord North Street in Westminster, were invariably interesting: a reflection of the shared belief that Conservatism amounted to more than the electoral face of self-interest and that Conservative ideas, seriously under-represented in British universities, drew upon a rich and vibrant intellectual tradition. (I remember Sir James Goldsmith, the billionaire founder of the Referendum party, bringing along his young son Zac to hear the debates.) But the night of Lamont's speech - the gist of which had been leaked to the media - was the only gathering that attracted television crews and photographers, who waited on the pavement for reaction. The atmosphere within crackled with excitement, Lamont's features twitching like a mischievous badger.
This was the twilight of the John Major era, the long goodbye to a generation of Tory government. Then, as now, Europe was dividing the Conservative party and a terrible reckoning lay ahead in the 1997 election. In practice, Black Wednesday in 1992 (the day when the pound fell out of the European Exchange Rate Mechanism) and the election of Tony Blair to the Labour leadership in 1994 had already done for the Tories. But they still had little collective sense of the electoral calamity in store.
By the time his party returned to office in 2010, Lamont's former special adviser David Cameron had been its leader for more than four years. In the interests of electability, he had urged his fellow Conservatives to stop "banging on" about Europe - a plea that they had respected, up to a point. But only up to a point. Thanks originally to Lamont - Cameron's former mentor - the possibility that Britain might leave the EU was now emphatically back in play. It was only a matter of time before it would rock his government to its very foundations.
It has taken 22 years for this simple idea - that we should withdraw from the EU - to grow to its present scale: we are eight days from a vote that could make real what Lamont made thinkable. The leave campaign has focused to a depressing extent upon immigration. But the case for departure has deeper intellectual roots that cannot be dismissed as mere nostalgia, xenophobia or reactionary reflex.
The idea of Brexit has become part of the warp and weft of contemporary politics. The question, surprisingly unexplored, is: how?
Long before it was so, Tony Blair believed that the true intention of the Tory Eurosceptics, whatever they claimed to the contrary, was always to get out of Europe. Though most of them insisted that their ambitions were confined to "renegotiation" of Britain's membership terms or the partial "repatriation" of UK sovereignty, Blair was sure that this was a ruse: the Tories' true objective was to liberate the nation from the EU's clammy grip.
When Blair took office in 1997, this was definitely not yet the case. His own enthusiasm for the EU, and impatience with whatever "forces of conservatism" stood in his way, clouded his judgment. In practice, his management of the "European question" was a petri dish that created the environment for hostility to the EU to flourish among Tories. By the time he left office in 2007, a great many Conservatives had concluded that the European project was irredeemable and that exit was the only sensible option.
Chancellor of the exchequer Norman Lamont arriving at the Treasury on Black Wednesday. Photograph: Adam Butler/PA Archive/PA Photos
It is easy to forget that Blair's unambiguous intention when he became prime minister was to take Britain into the very heart of the EU, not least by joining the single currency. In 2002, he told the Labour conference: "The euro is not just about our economy, but our destiny."
Gordon Brown, of course, did not share this dream, and successfully thwarted Blair's ambition to take Britain into the single currency. Where Blair saw poetry in the European project, Brown saw only prose. But, for a decade, the occupant of No 10 was a fervently committed EU-phile. This was bound to have dramatic consequences for the politics of the opposition and the emerging shape of conservatism in the early 21st century. The more passionate he became about Britain's role in the EU, the more convinced Eurosceptics became that the process of integration was spinning out of control and must be halted - by exit, if necessary.
A cohort of young Conservatives began to argue, with an intellectual coherence that could not be ignored, that Britain would be better off outside the EU. The two most prominent representatives of this tendency within the Tory movement were Daniel Hannan, an MEP since 1999, and Douglas Carswell, who has been an MP for Harwich and then Clacton since 2005. Carswell became Ukip's first member of parliament in 2014, after his defection from the Conservatives forced a byelection in his constituency.
Rather than objecting to the EU on reactionary grounds, Hannan and Carswell argued that it was not modern enough. In the 21st century, as technology tranformed the way we live, they asserted that voters would demand devolution and decentralisation, accountability and transparency. Against this political and cultural backdrop, the EU was hopelessly out of date.
This was the beginning of the Vote Leave movement (both Hannan and Carswell now sit on its campaign committee). What is under-appreciated is the extent to which it was a response to the Blair years, an intellectual counter-revolution.
Much of its energy was generated by Blair's conspicuous refusal to consult the electorate on the ratification of EU agreements. The treaties of Amsterdam (1997) and of Nice (2001) were significant steps along the integrationist path, but did not trigger plebiscites in this country. By the time the EU constitutional treaty was signed in Rome in 2004, the pressure for a referendum was immense - and not confined to the Tory benches. Here, after all, was an international pact that dramatically changed the rules on qualified majority voting (as opposed to the system where a single nation could veto a proposal), gave legal force to the EU's charter of fundamental rights and extended the EU's power into areas such as energy and space policy.
At first, Blair resisted the idea of a referendum, but in April 2004, he dramatically changed his mind. "It is time to decide whether our destiny lies as a leading partner and ally in Europe or on its margins," he said. "Let the issue be put and let the battle be joined." Blair believed that he could take on the Eurosceptics and secure Britain's position in Europe once and for all. Alas for him, the plan was scuppered by referendums in France and the Netherlands, both of which rejected the treaty and sent the EU's draftsmen scurrying back to their drawing boards.
By the end of his premiership, Blair, one of his closest allies told me at the time, felt a true "sense of loss" over Europe, close to a bereavement. I recall attending a speech he gave at St Antony's College, Oxford, in 2006 as part of his unofficial extended farewell tour. By now, there was no talk of "destiny"; only an admission that the political class had "locked [itself] in a room at the top of the tower", fretting over rules when it should have been busily winning hearts and minds.
That speech, a decade ago, was an elegy to a dream. It was part-cheerful, part-rueful, Blair's way of saying adieu to his European vision. What he did not sense was that the subterranean forces unleashed during his long premiership would coalesce in the next decade and bring Britain to the brink of leaving the EU.
Each of the parliamentary Brexiteers has his or her own story. Sometimes, it involves a slow, incremental disenchantment. In other cases, the moment of rejection was clear and identifiable. In spite of his long association with the case for withdrawal, Douglas Carswell falls into the latter category.
"I remember quite vividly," he told me earlier this year. "For me it was the failure of Blair. I was at the time working for a pan-European fund-management group. Everyone around me said that the euro was a good thing, the Lisbon agenda [devised in 2000 for economic reform of the EU] looked like it was really going to finally change Europe, and make it flexible. They talked about it being the most dynamic part of the world economy by 2010. Blair had so much political capital, not just domestically but internationally." His inability to translate that cachet into hard reform tipped Carswell into a firm commitment to Brexit.
Theresa Villiers, the Northern Ireland secretary, described a more gradual process of disillusionment. "When I was selected as a candidate for European elections back in 1998, I was certainly sceptical about the European project. But at that stage I wouldn't have thought seriously about leaving the EU - it just didn't seem to be on the agenda. My thinking was: we just have to make the situation work, get the reforms we need, and try to push the EU in the direction which focused on trade and business, and away from grand political projects."
Experience of the European parliament and commission gradually convinced Villiers that the EU's institutions and culture were beyond repair. "Whatever the question, whatever the problem, whatever the crisis, the answer was more Europe, more EU, more political integration," she recalled. "For decades we've had people in the Foreign Office saying Europe is coming our way, we've changed its direction, we've got opt-outs. And it just became abundantly clear to me that we were never going to win that argument in Europe."
Slowly, steadily - mostly as individuals rather than as groups or factions - Tory MPs were drawing the same conclusions, deciding that the EU was beyond redemption. Ken Clarke, the former chancellor, and Michael Heseltine, remained stubborn evangelists for the EU ideal. But they had not persuaded a younger phalanx of Tories to follow their path. Conservative opinion reflected a spectrum of opinion from diffident Euroscepticism to full-throated champions of Brexit.
When he became Tory leader in December 2005, David Cameron perceived the issue as entirely managerial. The eurozone crisis had ended any prospect of Britain joining the single currency, so it was not hard for him to assert that sterling was safe as long as he was in charge.
Among senior Tories the overriding fear, however, was more prosaic: namely that the next Conservative prime minister would face the same problems as John Major, beholden in the Commons to a group of hardline Eurosceptics who exploited the parliamentary arithmetic to push the prime minister further than he wanted to go on European matters or in other areas of policy. Daniel Finkelstein - then an adviser to William Hague, now a Times columnist and life peer - used to joke that the Tory Eurosceptics "wouldn't take 'Yes' for an answer."
Cameron certainly didn't want his premiership to be hobbled in that way. He also didn't want to entrench voters' fears that Tories were idiosyncratic, sectarian, and fixated by oddball priorities rather than those of the electorate. When Cameron told his party to stop "banging on about Europe" in 2006, he was issuing a warning about discipline and collective priority rather than unveiling a policy.
Douglas Carswell, the UKip MP for Clacton and leading Brexit campaigner. Photograph: Richard Saker for the Observer
In this respect, the hung parliament delivered by the 2010 general election spared him the fate that Major had suffered. As a governing partnership with the Liberal Democrats became a realistic prospect, Cameron was heard to remark that coalition with Nick Clegg was probably preferable to being in "coalition with Bill Cash", the passionately sceptical MP for Stone, Staffordshire, and chair of the Commons European scrutiny committee.
As the Cameron-Clegg government found its bearings, the number of Brexiteers on the Tory benches was not immediately apparent. The new PM had already kept his promise to withdraw his party from the centre-right grouping in the European parliament, the European People's party. In June 2009, Hague, back in the frontline as one of Cameron's closest lieutenants, had announced the formation of the European Conservatives and Reformists (ECR), an explicitly "anti-federalist" bloc initially composed of 55 MEPs.
Naturally, this was welcomed by sceptical Tories. But it did not really compensate for a much greater grievance - specifically, the failure to hold a referendum on the treaty of Lisbon. This pact, signed in 2007, was essentially a reheated version of the constitutional treaty, presented with less pageantry and pomp. You did not have to be a Euro-anorak to spot that any country that had promised a referendum on the constitutional treaty should offer one now. Yet, as prime minister, Gordon Brown decided not to make such an offer.
In September 2007, Cameron had written an article for the Sun, offering the punters "this cast-iron guarantee: if I become PM a Conservative government will hold a referendum on any EU treaty that emerges from these negotiations."
In November 2009, it became clear that the treaty of Lisbon was going to be ratified by all 27 member states, entering EU law, and Cameron concluded that his pledge was no longer binding. For a while, Hague had offered a new promise - still opaque - that he and Cameron would not "let matters rest there" if the treaty was thus ratified.
The strategy was both ambitious and perilous. First, there would be a referendum lock on significant transfers of sovereignty to Brussels in the future - an objective achieved in the European Union Act 2011. Second, there would be an audit of the balance of power between Britain and the EU. Third, on the basis of that audit, the prime minister would renegotiate Britain's terms of membership. And, fourth, there would be an in-out referendum on the deal he had struck in Brussels.
Immense thought and energy were expended upon this plan, which was announced in its entirety in January 2013 at Bloomberg's London HQ. As the leave cause has improved its position in the polls, I have been struck by the number of people who now claim - or let it be known that they claim - that they tried to talk the prime minister out of embarking upon this rocky and potentially self-destructive path.
As so often, George Osborne was the person in the room who articulated the truth, palatable or not. "The referendum genie is out of the bottle," he said in private around the time of the Bloomberg speech. What he meant was that the cycle of agitation for such a vote, followed by the government of the day's refusal to oblige, could not go on indefinitely.
Nor could Cameron afford to be seen as untrustworthy - by the voters, or by his backbenchers, many of whom were antagonistic towards the coalition. The unapologetic Europhilia of Nick Clegg nurtured the Euroscepticism of the average Tory MP. So what if Lisbon was already written into EU law? Couldn't its content be removed if the British people were given their say and rejected the treaty? And why was Clegg allowed a nationwide referendum in 2011 on the marginal issue of the alternative vote, while Tories were denied a vote on a sweeping EU deal?
If the Blair years had spawned an intellectual counter-revolution, the coalition helped it spread. In October 2011, a motion submitted by David Nuttall, the Tory MP for Bury North, came before the Commons, thanks to a new system that granted parliamentary time to online petitions that had secured more than 100,000 signatures and then been chosen by the backbench business committee. The Nuttall motion called for a referendum on Britain's membership of the EU.
What followed was a hint of the disciplinary breakdown that has engulfed the Conservative party at every level during the current campaign. The motion was not binding and might have been an opportunity to allow backbenchers, frustrated by the constraints of coalition, to let off steam in a free vote. Instead, Cameron imposed a three-line whip. The mayhem that followed did the prime minister and his EU strategy no favours at all, and revealed that, where Europe was concerned, MPs' loyalties were very unclear.
Leading Brexiteers Iain Duncan Smith and Theresa Villiers. Photograph: Reuters
It was at this point, for instance, that George Eustice, formerly Cameron's press secretary, emerged as leader of the Fresh Start group of Eurosceptic MPs. These Tories were mostly young and, in almost every respect, faithful to Cameron's cause. But they took a different view of the EU and Britain's role in it. Behind the scenes, Steve Hilton, one of Cameron's closest advisers and friends, had concluded that Britain needed to get out of the EU as soon as possible, lest our spirit of enterprise and creativity be strangled by red tape.
At this stage, Cameron remained confident that his renegotiation of Britain's membership would bring around such allies. In this respect, he gravely underestimated the commitment to Brexit that was spreading in his tribe. On the lookout for political mischief, Cameron was paying insufficient attention to the genuine dilemmas facing those who wanted to be loyal to him.
The intellectual ancestry of leave has much more intellectually coherent roots than Farage's pound-shop Anglo-Trumpery
In recent months, we have grown used to speculation about what will happen to Cameron if he loses. A favourite parlour game in the Westminster village right now is to name Boris Johnson's first cabinet, and to ponder which role Michael Gove might occupy. But the experience of those Brexiteer Tories who have no ulterior political motive, such as Villiers and Hilton, is more compelling than of those who are using the campaign as a lever to displace Cameron. Villiers manifestly abhors the reduction of government to light entertainment and hates opposing her boss. Yet she and thousands of Tories like her believe that they cannot support their prime minister when he needs them most.
In a party that still notionally venerates loyalty and takes seriously the claim of the incumbent leader to his or her party's support, the pursuit of an outcome that may destroy a premiership is a huge deal. How have they reached this point?
If leave wins on 23 June, it will be a victory for Nigel Farage. As the referendum has approached, the closing argument of the Brexiteers has been shockingly focused upon the supposed ill effects of immigration, and the misleading argument that leaving the EU will resolve those problems at a stroke. That is the high-carb political junk food on which the leavers have been feeding the nation. It is the old Ukip trick - xenophobia disguised as constitutionalism - and at the time of writing, it is gaining ground.
Yet the intellectual ancestry of the leave cause has much more interesting and coherent roots than Farage's pound-shop Anglo-Trumpery. The argument of the more thoughtful Brexiteers is that postwar, post-Thatcher Britain has reached a point of economic strength, cultural maturity and confidence that enables it to be weaned from the unreformable EU.
"We are very keen to put a positive case," Villiers told me. "In many ways joining the EU in the 70s was an admission of defeat based on the assumption that we were destined in this country for perennial decline. Now you look at our economic performance compared to Europe and we are performing much better than the bulk of eurozone countries."
Carswell goes further: "I'd say Euroscepticism is a product of modernity. It's a rational response to a changing world and it's born of hope that actually things can be better. So if the vote goes leave's way on the 23rd we'll look back on the period between 1973 [the year the UK joined the EU] and 2016 as a sort of exceptional period."
The irrepressibly optimistic MP for Clacton sees the yearning to leave the EU not as a foetal cringe by old-fashioned voters but precisely the opposite. "It is absolutely not English exceptionalism, this is not John Bull nationalism. On the contrary, I would say that modernity makes those ideas look more ridiculous than ever ... The European project is based on the idea, 'Restrict your freedoms and your liberties and your sovereignties and leave it to us, we'll manage.'"
Why has the idea of Brexit suddenly gathered pace? Farage would probably attribute the success of his party and its central argument to "mass immigration", as if the EU were the sole agency that determines this most complex of policy questions. Carswell - notionally in the same party as Farage, though you would never know it - suggests that a convergence of forces has suddenly conspired to make leaving the EU seem, to many, like the best course of action.
This is how radical change happens, according to Carswell. "I remember working on an archaeological dig in Europe in the late 80s, and a German woman my age telling me that East Germany would never be free. Within five years, it was. I remember growing up in Uganda [where his parents were doctors] and people telling me that apartheid would take at least 30 years to crumble - it was gone within a decade. When something very significant happens - which Brexit will be - the forces animating change conspire very fast."
As he makes his case that Britain could do better if it were free, the unexpected exhibit is the 2012 Olympic Games. "I was slightly curmudgeonly [at the start]," he told me. "I'd just been elected as an MP when we put in the bid for the Olympic Games and like lots of people I thought, 'Oh gosh, it's going to make London crowded and it's a lot of money'. And then it started and I thought, how wrong I was - wow, we can celebrate what a great country we are. It really lifted and I think that's the atmosphere and the vibe that will come out of 23 June."
For those engaged in the struggle to free Britain from the EU, this is more than another campaign. If they lose on 23 June, the battle will go on, in guerrilla form and in referendums on specific EU treaties.
When I visited Matthew Elliott, the CEO of Vote Leave, he was planning Take Control Day for 12 March. There was a time when Eurosceptics agonised about "sovereignty", sounding like the jurists and lawyers that many of them were. Their objective was the "repatriation of powers" - a menacing phrase that meant little to voters. The new generation of Brexiteers has settled upon the friendlier notion of "control" - a word that deftly links the geopolitical with the personal.
As much as anyone, Elliott, who is 38, has been the figure giving the case for departure organisational and intellectual coherence. His partner in crime is the brilliantly contentious Dominic Cummings, a former special adviser to Michael Gove. Elliott's job has been to maintain discipline on the leave side, and to ensure that the campaign nurtures optimism, not anxiety - though the politicians fighting the battle on the frontline have not always obeyed.
Matthew Elliott, the head of Vote Leave Photograph: Peter Nicholls / Reuters/Reuters
The HQ of Vote Leave, where, at this point, 35 of its 55 staff were based, is in a modern building on Albert Embankment. Bespectacled, rangy and calm, Elliott comes across as the very opposite of a flame-eyed ideologue - more as a prosperous investment banker who has not let his mews house in Chelsea go to his head. In fact, he is one of the most experienced - and successful - single-issue campaigners in the UK. It was largely Elliott's strategising that secured such a decisive victory for the campaign to reject the adoption of the alternative vote system in 2011 - only the second nationwide referendum to be held in the UK. His specific insight was to grasp early in that campaign that Labour voters would decide the result, which proved to be the case, Since then, he has been intermittently preparing for the third such plebiscite.
The establishment of the group Business for Britain - a coalition of sceptic businessmen founded in April 2013 - reflected an early recognition by the Brexiteers that they had to be in a position to deny from the start remain's inevitable claim that business was foursquare behind continued membership of the EU. Without Business for Britain, said Elliott, "we'd be in a situation where people would still be saying that business is basically united behind remain and we'd [only] be able to get out a few business folk. The media story would be 'Businesses for remain.'"
It was equally important that the leave campaign not resemble a committee of the fringe. Its claims needed to sound like common sense, not the fist-waving slogans of peripheral ideologues. In 1975, the out campaign attracted figures who were regarded as extreme: Enoch Powell, Tony Benn, the leaders of the National Front. "We've managed to set up a platform which has attracted some serious people," said Elliott. "Had it not been for Michael [Gove] and Boris [Johnson] you might have expected, for argument's sake, 50 to 70 Tory MPs to be on the leave side." According to the BBC website, at the time of writing 150 MPs had declared in favour of the leave campaign.
Related: Brexit will hurt your city, Labour tells core voters - but no one's listening
To stand a chance of winning, Vote Leave has had to transform - or at least try to transform - the way in which Brexiteers are perceived by the public. The campaign cannot look like a heritage organisation, preserving an endangered version of Britain from extinction or vandalism. It must reverse the usual polarities of this debate, making the remain camp look old-fashioned and sentimentally attached to an idea of Britain's place in the world that is hopelessly out of date and quite unsuited to the 21st century.
Like Carswell, Elliott believes that Britain's role in the EU could have been salvaged had Brussels itself recognised how it is being changed by the headwinds of history. "I think naturally the EU is breaking up into being the more centralised eurozone versus the non-eurozone member states. So to have non-eurozone member states with a looser trade-based relationship was feasible - and is actually where I think the EU is generally going." But instead of pushing for a genuinely two-tier Europe, says Elliott, Cameron accepted crumbs from the Brussels table and called it a "special status". This transaction dramatised the leave message at the perfect moment, argues Elliott. It made the voters wonder what they were getting for their £350m a week (or £136m as the Guardian's referendum reality check calculated).
Related: Why Vote Leave's £350m weekly EU cost claim is wrong
It is striking that Elliott does not deploy the familiar argument that we were duped or misled in 1975. His argument is more sophisticated, and concedes something to the other side. Back in the 1970s, when Britain was weakened by industrial decline, inflation and union strife, it needed the protection of the EEC and membership of the club. According to this view, the electorate was right to vote for "in", and decisively so. But, 41 years later, different conditions prevail, and Britain no longer requires the crutch of this costly alliance. If there is such as thing as the spirit of the age, it is at odds with the idea that unelected bureaucrats in Brussels and judges in Luxembourg have aggregated so much power over our lives. The EU was founded in an age when the idea of taking power from elected demagogues and fiery orators and giving it to dull bureaucrats had much obvious appeal. But now, in 2016, the children and grandchildren of the generation that fought in the second world war expect accountability, transparency and the ability to sack those in government who let them down.
On the day that I saw Elliott, the papers were full of allegations - later convincingly denied - that Sir Jeremy Heywood, the cabinet secretary, has been denying key papers to senior ministers who support Brexit. Elliott was in no doubt: "If this turns into a referendum between the establishment and the people, we will win. By miles."
In the history of ideas, context is all. In the last days of this contest, the leave campaign is concentrating remorselessly upon immigration - its prime doorstep issue. But there is a broader setting, too: the embrace of Brexit by a significant tranche of the political class reflects despair with the EU, matched, more interestingly, by a faith in Britain's ability to go it alone and a conviction that the 21st century will favour nimble states over cumbersome bureaucratic blocs.
Those who seek such a role for this country no longer define Britain's place in the world by its presence at all its top tables, from the UN security council to the G8 to the EU itself. They envisage the millennial UK as something closer to a buccaneering galleon, unrestrained and versatile. Whatever else may be said about this declaration of independence, it has little in common with the calls for parliamentary sovereignty to be restored that defined the case for withdrawal in 1975. Even if leave loses on 23 June, the aspiration it reflects will survive, and live to fight another day.
Even in his most grandiose moments, I doubt that Norman Lamont can ever have imagined that the idea he pulled out of the deep freeze would flourish as it has. In his memoirs, the former chancellor recalls how he was shunned at the 1994 conference after his speech questioning Britain's membership of the EU - and by whom. "The next person I saw," he writes, "was David Cameron, my former special adviser at the Treasury, who cut me dead."
Revenge takes many forms.
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