It is an office distinguished only by its utter lack of distinction: rectangular, low-ceilinged, strip-lit, a wall of windows down one side and three long tables across the middle. Two or three dozen young, casually-dressed men and women work at their screens or talk on mobiles – nothing so archaic as landlines here. Otherwise there’s a photocopier, a solitary pot plant and just the odd clue about the purpose of this room – the blue and gold-starred European Union mini-flag on one desk, and the two banners on the otherwise bare walls. “Healthier In”, one proclaims. “Scientists for EU”, the other declares.

Improbable as it might seem, this is the nerve centre of the campaign to prevent Britain leaving the EU. It is a den of “Remoaners”, “saboteurs”, “mutineers”, “wreckers” and, some would contend, incurable optimists. Their chances of success are slim, but their strategy – to secure a “people’s vote” on the government’s final Brexit deal – offers the only plausible chance of reversing what they and millions of others regard as the looming catastrophe facing Britain.

The office is on the first floor of Millbank Tower, the steel-and-glass edifice overlooking the Thames barely half a mile from the Palace of Westminster. It was from this building that Labour plotted its path to gaining power in 1997 and that the Conservatives won it back again in 2010. James McGrory, executive director of a group called Open Britain, says those victories would pale beside a reversal of the 2016 Brexit referendum: “I don’t think it would be an overstatement to say it would be one of the biggest shocks in modern British political history to pull off what we are trying to achieve.”

A sparky, blue-eyed, ginger-haired north Londoner, McGrory, 35, knows all about victory and defeat – particularly the latter. He was chief spokesman for Nick Clegg during the coalition government of 2010-15 and subsequent general election in which the Lib Dems were annihilated, and for the Stronger In campaign during the referendum. He remembers leading his devastated team to a pub in Smithfield meat market as dawn broke after that referendum defeat, watching an exquisite sunrise over St Paul’s Cathedral and thinking of the shock that his friends and relatives would face when they woke up an hour or two later and learned the result. He resolved to keep fighting, he says, “so that when my kids ask me what I did I can say I grafted 18 hours a day for what I believed in, and tried to make my country a better place”.

The anti-Brexit campaign has verged on the shambolic in the two years since that referendum. It has been waged by such a bewildering plethora of groups that they have invited mocking comparisons with Monty Python’s assorted Judean People’s Fronts. They have duplicated each other’s work. They have been hobbled by rivalries and inflated egos. There have been tensions between the grass roots and top-down organisations, and between those run by the tarnished veterans of the referendum campaign and by the newcomers. There was a very public spat over whether to cancel a “Unite for Europe” demonstration in central London following the Westminster terror attack in March last year.

The deepest divide has been between outsider groups such as Best for Britain that are determined to stop Brexit, and those with close parliamentary links such as Open Britain that have been fighting to mitigate it. Eloise Todd, the Yorkshirewoman who runs Best for Britain, argues that a soft Brexit would turn the UK into such a “vassal state” of Brussels that a hard Brexit would inevitably follow in a few years’ time.

“Just as the government didn’t have a plan for Brexit, so our various different groups didn’t have a plan for fighting it,” Hugo Dixon, the wiry, cerebral former Financial Times journalist who runs a group called InFacts, admits. The post-referendum period was “a desert”, he says, albeit one with a few “oases”. Whenever he spoke at meetings around the country, “the strongest message coming out of them was, ‘Please, get your shit together’”.

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That is finally beginning to happen. A disparate rabble is slowly mutating into a coherent force with a single, agreed objective. But with barely five months left until parliament votes on whatever exit deal – if any – the government manages to negotiate, it has precious little time.

In March, eight of the most prominent groups moved into this new shared office in Millbank Tower, with immediate and felicitous results. They now speak directly to each other. They co-ordinate better. They bounce ideas off one another, and agree on lines to take or messages to disseminate through the press and social media. Every Wednesday morning they meet as a “grass-roots co-ordinating committee” to plot strategy with Labour’s Chuka Umunna, and the Conservatives’ Anna Soubry and other leading parliamentary opponents of Brexit. They are jointly planning what they hope will be an enormous pro-European demonstration in London on 23 June – the referendum’s second anniversary. They go to the pub together after work.

“It’s made a huge difference, it really has,” says James MacCleary, campaign director of the European Movement. “In an era of technology, when we’re supposed to connect through digital means, it’s incredible how useful it is to be physically located in the same place. There’s no replacement for being able to pop over to someone’s desk and say, ‘I’ve got this idea. What do you think?’”

On the night of the referendum MacCleary, 37, a former Lib Dem campaign official who returned to the political fray after working for the RSPCA, apologised to his three-month-old son. He has continued to fight Brexit because, “I can’t bear the idea of having to explain to Elliott 15 years from now why he doesn’t have the same opportunities I had as an EU citizen. I want to be able to tell him I did absolutely everything I could.”

A synergy of sorts has begun to develop between the groups as they seek to rally public support and embolden Remain-minded MPs terrified of incurring the tabloids’ wrath. InFacts provides data and research, and publishes a succinct daily analysis of Brexit’s latest twists and turns. Open Britain, besides boasting more than 560,000 Facebook followers, is strong on media and communications. The European Movement and Britain for Europe provide a network of roughly 150 local groups that man stalls, hand out leaflets and lobby their MPs.

Scientists for EU and Healthier In the EU, which represents doctors, nurses and midwives, are social media experts. Our Future Our Choice and For Our Future’s Sake reach out to the young.

Though Best for Britain has not moved into Millbank, it supports the groups that have. Operating from a former bakery in Covent Garden, it provides funding (it received £400,000 from George Soros in February, and a further £220,000 from the philanthropist and outraged members of the public after the Daily Telegraph smeared him in an article by Nick Timothy, Theresa May’s former chief of staff). It runs advertising campaigns with the slogan “When will we know what we voted for?”, as well as “barnstorm sessions” that train grass-roots activists in the art of persuasion.

The move has also raised the campaigners’ spirits. “For a couple of years I was working in my living room at home, so coming in here and having this feeling of everyone working together certainly boosts morale,” says Rob Davidson, 38, the bearded, Scottish co-founder of Scientists for EU and Healthier In.

Even more importantly, the groups have finally united behind the single demand that they unveiled in April: that the people should have the final say on whatever Brexit deal May’s government strikes with the EU.

The “people’s vote” is a clever concept developed after much polling and focus-group research. It can be presented as an entirely new vote on the detailed consequences of Brexit – not a second referendum on the broad principle of leaving, which would, says McGrory, be “utterly, utterly toxic”. The “soft Brexiteers” and “no Brexiteers” of the anti-Brexit movement can unite behind it. Moreover, the “hard Brexit” zealots of the Tory right would find it hard to object to such an exercise if they really believe in the “will of the people” and the popularity of their cause.

Indeed, proponents of a people’s vote argue that some Brexiteers might welcome the chance to reject a deal that falls short of their desire for a clean break with Brussels. “There are Leavers who may be unhappy with the deal because they were promised a unicorn, a tortoise in every home and bananas in bunches of 11, and they’re not going to get that because it’s bullshit,” McGrory says.

On the face of it, the people’s vote campaign stands scant chance of success. It lacks a single articulate, charismatic leader. “If we had the equivalent of a Barack Obama who said ‘Yes We Can’ and people believed him it would be over and done with,” says Dixon. The movement is fighting a profound public fatigue with Brexit, a reluctance to reopen such a bitter and polarising dispute, and a widespread sense among voters – including many Remainers – that the battle has been lost and the country must move on. “It’s not a done deal, but people think it is because the Labour Party, the Conservative Party and the BBC say it is. It’s a self-fulfilling prophecy,” Dixon complains.

The right-wing press continues to pump out pro-Brexit propaganda. MPs are terrified of resisting Brexit for fear of being denounced on the Daily Mail’s front page. The economy has faltered but not imploded. In two years – despite the manifest unravelling of the Brexiteers’ promises and the government’s grotesque mishandling of the withdrawal negotiations – the opinion polls have barely moved: from 52-48 in favour of Brexit to, at best, 48-52 against. Time, moreover, is running out.

On top of all that, a remarkable sequence of events would be required for a people’s vote to happen. The Commons would have to reject the government’s Brexit deal when it votes on it in October or – more likely – November, and that would require almost every Labour MP plus at least a dozen Tories to vote against. Many Labour MPs represent constituencies that voted Leave.

Parliament would then have to pass legislation to approve another plebiscite, and for that to happen Jeremy Corbyn – who regards the EU as a “capitalist club” – would have to abandon Labour’s official opposition to the idea. And because such a vote would take at least six months to organise, all of the 27 other EU member states would have to agree to extend Britain’s membership beyond its scheduled expiration on 29 March next year.



Chuka Umunna, who meets regularly with Remainer groups, in front of a “Brexit Facts Bus” earlier this year

Charles Grant, director of the Centre for European Reform, is sympathetic to the people’s vote campaigners, but he sees little chance of any of the above happening and gives them just a “1 or 2 per cent chance” of stopping Brexit. He concedes that a dramatic shift in public opinion – to, say, 60-40 against leaving the EU – could change the dynamics, but cannot foresee such a change. He fears that too many of the campaigners are “naively optimistic” London-based members of the middle-class liberal elite who are simply preaching to the converted.

Though the campaigners concede that they face an uphill task, they are considerably more optimistic than Grant. They enjoy playing the role of insurgents confronting what is now a Brexit establishment. They claim that their support is growing (nine northern Labour MPs have recently backed them) and that fund-raising has never been easier (they reached their target of £100,000 for the 23 June demonstration in barely a week). They point to the extreme volatility of present-day public opinion, and to polls showing that more and more people believe Brexit will be bad for the economy and the NHS even if the headline figures have not changed. “The hope is that now we have our act together we will be able to shift public opinion more rapidly than it has shifted in the past,” says Dixon.

They also see a deeply divided and inept government that is unable to agree its own negotiating position, let alone one that the EU might accept. They have watched the House of Lords defeat the government no less than 15 times on the EU Withdrawal Bill, and seen the Labour leadership edging towards a softer Brexit. They claim it was pressure from their supporters that secured a crucial four-vote victory in December 2017 for Tory Dominic Grieve’s amendment giving MPs a “meaningful vote” on the final deal.

The anti-Brexit campaigners claim the momentum is all on their side. “There’s now a feeling that we have a fighting chance,” says Dixon.

“A year ago you got a lot of ‘I voted Remain but what can you do?’ Now we get a lot more people going ‘Yes, there must be a way of doing something about this’,” says MacCleary.

The polls also show rising support for a people’s vote – 53 per cent in favour to 31 per cent against, according to a recent Opinium survey – and that should encourage moderate Tory and Labour MPs to back the idea. “There’s a lot of them who want to do the right thing, but they need to have the wind at their backs,” says Todd, head of Best for Britain. But whether there would be majority support in parliament is another matter.

It is certainly possible that MPs will reject the government’s deal this autumn. Indeed, at present it is hard to imagine a deal that could command a majority, given the deep rift within the Conservatives’ ranks and the likelihood that most Labour MPs will vote against it. That said, the deal is likely to be long on aspiration and short on detail, and the government will put immense pressure on the Tory rebels to fall in line.

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If the Commons does reject the bill, various things could happen. Britain could crash out of the EU without a deal, though the risks and costs would be enormous. Theresa May could seek a new election, but she would have to secure the two-thirds majority required under the Fixed-Term Parliaments Act. Would Tories support a move that could let Corbyn into Downing Street when they do not need to go to the country until 2022?

May might resign, but it is unlikely that her replacement – presumably a robust Brexiteer – would have any more success. Or she could seek further negotiations with Brussels, but it is far from certain that the 27 other member states would all agree.

“Some would say that the alternative is a cliff edge which is bad for us and bad for them, so we’d better give them an extension. Some may say, ‘Oh for God’s sake, we’ve had enough of this,’” suggests Lord Kerr of Kinlochard, a leader of what he jokingly calls a “revolution led by Zimmer frames” in the upper house.

Kerr is another die-hard opponent of Brexit. As UK permanent representative to the EU in the early 1990s, he saw his European counterparts snap to attention when they suspected he was talking for Washington, DC. As British ambassador to the US from 1995 he enjoyed plenty of face time with President Bill Clinton because the UK was so influential in Europe. “I know that we cut much ice in the rest of the world when the rest of the world thinks we cut ice in Brussels,” he says.

The other possibility is that the government, or a parliament that dislikes the deal but is reluctant to be seen thwarting the “will of the people”, decides to seek the country’s opinion through a second referendum. Grant, of the Centre for European Reform, all but rules that out. He argues that May wants to be “the prime minister who delivered Brexit” and that she would be “crucified” by right-wing Tories for jeopardising their historic victory in the 2016 referendum. “I think they’d rather have Jeremy Corbyn in Downing Street than risk a referendum that could keep us in the EU,” he says.

Kerr disagrees. He believes a people’s vote would offer Corbyn a way of holding his party and its supporters together. As for the Tories: “If they believe what they say, that the country really wants us out, they can go and campaign for their deal and believe they are going to win. If they don’t win they know that’s the end of Theresa May and they’re still in government. It’s better than an election because they don’t risk losing power.” Kerr disputes the idea that the quest for a people’s vote is quixotic and hopeless. He gives it a 30 per cent chance of success. “My belief is that we will end up with a second referendum. I am quite bullish about that,” he says. He adds quickly, however, that he has no idea whether the country, given a second chance, would decide to stay in the European Union.

On the one hand, the Remain campaign could hardly be as inept as it was last time, the Europhile young would vote in much greater numbers, and the Brexiteers’ promises have mostly proved vacuous. On the other, millions of Britons would be angry at being asked to vote again, blame a bullying EU for not giving us a better deal, and contend that the Remain campaign’s predictions of disaster have not materialised. “Public opinion might shift in the wrong direction,” Charles Grant warns. Or, put another way: while the people’s vote campaign could yet win the battle from its new Millbank command centre, it could still lose the war.

Martin Fletcher is a New Statesman contributing writer