Mark Malloch-Brown is drawing me a picture. He first saw a version of it 28 years ago, while working on Mario Vargas Llosa’s presidential campaign in Peru. In a Lima bar one night, Malloch-Brown’s fellow consultant Rob Shepardson flipped over a beer mat and drew two intersecting axes that, he said, summed up all political campaigns. In Malloch-Brown’s version, the vertical axis runs from “change” to “status quo” and the horizontal from “distrusted elites” to “people like me”.

“Where was the Brexit campaign? Up here.” He marks a cross in the top right corner. “And where was the remain campaign? Down here.” Another cross, bottom left. “How do we reverse that position? How do we make remain – the very word is a status quo word – the change cause, and find spokespeople to deliver that message? Our whole campaign is about how to get to here.”

We’re meeting in London on 8 February, hours after the Daily Telegraph published an inflammatory front-page story about a £400,000 donation made by the investor and activist George Soros to Best for Britain, the anti-Brexit organisation Malloch-Brown chairs. After a hectic day of interviews, he appears serenely unflustered. “One shouldn’t overreact to the drama of things like this,” he says, leaning back and opening a can of Coke.

He’s seen worse. The Labour peer’s CV includes the UN, the Foreign Office and election campaigns in “lots of very strange places where massive disruptive forces were at work”. He joined Best for Britain last September, charged with uniting the anti-Brexit movement, and went public on 17 December, promising “a much more coordinated campaign and a more coherent, consistent message”. On 1 February, the Labour MP Chuka Umunna formally announced the existence of the grassroots coordinating group (GCG), a regular Wednesday morning gathering of organisations, activists and sympathetic MPs. Two weeks ago, GCG members launched the People’s Vote, calling for a referendum on the final Brexit deal.

One GCG member describes Malloch-Brown’s intervention as an accelerant rather than a catalyst – discussions about a united front had been ongoing for months – but to most remainers, 18 months after the referendum the movement still appeared frustratingly diffuse. The plethora of groups with overlapping names – Best for Britain, Open Britain, Britain for Europe, the European Movement – inspired frequent references to Monty Python’s People’s Front of Judea. Nick Clegg complained: “It is frankly a gift to the Brexiters the way so much anti-Brexit energy is being dissipated in so many disorganised ways.”

Facebook Twitter Pinterest Mark Malloch-Brown of Best for Britain: ‘There’s a volatility about British politics.’ Photograph: Suki Dhanda for the Guardian

That is no longer the case. The new arrangement, which Malloch-Brown describes as a “ragged army” or “wild garden”, pools resources around a shared message, while allowing space for different opinions and achieving the broadest possible reach. This alliance has been achieved not a moment too soon. On 29 March 2019, under the terms of article 50, the UK is set to leave the EU, beginning a 21-month transition period. Having all but abandoned the sunlit uplands, the government’s most powerful argument now is grim inevitability: like it or not, it has to happen. The anti-Brexit movement insists this is not true, and it has only months to prove it. “If this was Britain in a more traditional, settled moment in its political rhythm, it wouldn’t be enough time,” Malloch-Brown says. “But there’s a volatility about British politics at the moment which is quite novel.”

Thwarting the most divisive and disruptive development in modern British history would be an extraordinary achievement. This is how the anti-Brexit movement plans to do it.

***

Thursday 23 June 2016 was one of the roughest nights of James McGrory’s life. As a seasoned Liberal Democrat operative, he had grown accustomed to disappointing nights, but this was the first time it had fallen to him, as chief spokesman for Britain Stronger in Europe, to address the defeated troops. There were tears. Alcohol was required. The nearest pub that was open at dawn was the Hope, opposite Smithfield meat market in central London. “If the irony of drinking somewhere called the Hope wasn’t enough, all these lads were coming in from their shift covered in blood,” he remembers. “There was a lot of gallows humour.”

Post-ballot analysis is a game of winner takes all. The losers’ shrewd decisions are swept aside along with the winners’ mistakes. The truth is more nuanced, but it is generally agreed the remain campaign was too conservative and establishment-dominated, while the leave campaign was more passionate and agile. “They were very good at characterising us: the elites and Project Fear,” McGrory says over coffee and cigarettes in the plaza outside Millbank Tower in Westminster, the anti-Brexit movement’s new riverside nerve centre.

With the country exhausted and divided by the referendum, McGrory had to decide what to do next. Under election law, dissolving Stronger In would have meant discarding its database of half a million email addresses. “It would have been silly to throw the greatest pro-European asset that has ever been established in this country in the bin,” he says. “The question was: how do we keep the flame alive?”

One demo, ironically named Unite for Europe, almost fell apart, split by personality clashes and fights over strategy

McGrory and his colleague Joe Carberry (who has since moved on) morphed Stronger In into Open Britain. Launching in August 2016 with six staff (since expanded to 11), the campaign group aimed to “seek common ground between voters on both sides” by advocating a Brexit so soft, one journalist dubbed it “the Mr Whippy of Brexits”. McGrory calls it the best argument available at the time. “We couldn’t just come out and say we didn’t agree with Brexit, because we’d just been beaten and it would have lacked credibility. Second, it wasn’t where the country was. And third, there was zero appetite in parliament.”

Still, Open Britain’s position struck many remainers as defeatist. Early attempts at unity were derailed by heated exchanges between people who immediately sought to reverse Brexit and those who favoured a more cautious, long-term strategy. There was friction at the grassroots, too. Although several regional groups coalesced into Britain for Europe, others butted heads. “There was a lot of chaos and a lot of new entries,” says Dr Mike Galsworthy, co-founder of Scientists for EU and Healthier IN the EU. “Because it was such a confusing landscape, different people’s strategies were hard to line up and would change over time.” One major demonstration in March 2017, the ironically named Unite for Europe, almost fell apart when the organisers fractured into two groups due to personality clashes and fights over strategy. “That got very toxic,” Galsworthy says. “When the march finally happened, everyone breathed a massive sigh of relief and said, we don’t want to go back to that again.”

“That year was a bit of a desert for us,” says Hugo Dixon, the activist who runs anti-Brexit factchecking website infacts.org. “We went into a vicious cycle. We lost almost all our parliamentary and media support. ‘Stop fighting, get real,’ was the message I would get. It became almost impossible to raise money; people thought, ‘What’s the point of backing a lost horse?’ As a result, the pro-European activists lost heart.” He brightens. “Then Theresa May did this wonderful thing of calling an election.”

When May sought a mandate for hard Brexit on 18 April 2017, Best for Britain was eight days away from its official launch. “We thought, ‘Crikey, either we pop our plans in the freezer and see if they’re still relevant on 9 June, or we engage,’” the campaign director Eloise Todd says. We’re sitting in Best for Britain’s central London meeting room, surrounded by unnervingly large satirical portraits of Boris Johnson, Michael Gove and Tony Blair. “We felt we had little choice but to engage.”

During the referendum campaign, Todd had been global policy director for the One campaign, the anti-poverty coalition co-founded by Bono. Before that, she worked in and around the EU, becoming friends with the late Jo Cox, another Yorkshirewoman who worked in Brussels and anti-poverty NGOs. “I was known for getting governments to agree to ambitious things they didn’t really want to do,” she says. “Being a gamekeeper turned poacher, you learn what changes politicians’ minds.”

Facebook Twitter Pinterest Eloise Todd of Best for Britain: ‘I don’t mind looking a bit foolish.’ Photograph: Suki Dhanda for the Guardian

Shortly after the referendum, the Labour MP David Lammy called Todd to ask for advice because he believed “Brexit would be a massive mistake” and “the remain campaign was on its knees”. He introduced her to people who were looking to set up a more robust alternative to the continuity remain campaign, including the former health minister Alan Milburn and the economist Anatole Kaletsky. She started work in January 2017. “There seemed to be a clear gap in the market, a democratic way through this,” Todd says. “We said, the government’s got a mandate to negotiate, but not to sign it off.”

Todd’s first attempts to ally with other groups fizzled out. “There was not a huge appetite; people wanted their own patch.” (“I don’t recognise that assessment,” McGrory says.) But Best for Britain and Open Britain launched tactical voting initiatives to topple pro-Brexit MPs and boost remainers. It looked like a tall order. Best for Britain’s private polling predicted a walloping Tory majority. “A senior pollster told me, ‘You shouldn’t be doing this. It’s not going to work,’” Todd remembers. “I said, ‘I agree it looks very grim, but I don’t mind looking a bit foolish, because the alternative is not to try at all.’”

If the expected Tory landslide had materialised, Todd says, “We would have shut up shop and gone home.” Instead, May lost her majority altogether. “OK,” Todd thought. “Game on.”

***

On election night, Chuka Umunna was “elated” by the implications for Brexit. May’s mandate for a hard Brexit had been emphatically rebuffed and it was now arithmetically possible to defeat the government in the Commons. A few days later, he met with Anna Soubry, the Tories’ remainer-in-chief and a close ally since the referendum campaign, and said, “Look, we’ve got to get organised.”

The result liberated Umunna, who had been mooted as a challenger to Jeremy Corbyn in the event of a Tory landslide. “A few people saw my involvement in the pro-EU movement partly through the prism of internal Labour party politics,” he says, drinking tea in his office at Portcullis House. “This is nothing to do with the Labour leadership. Brexit is bigger than that.”

Facebook Twitter Pinterest MPs Layla Moran (Lib Dem), Chuka Umunna (Labour) and Anna Soubry (Conservative) at the launch of the People’s Vote earlier this month. Photograph: Vickie Flores/Alamy Live News

Umunna is passionately pro-European. “I am a quarter Irish, I have a Danish niece, nephew and brother-in-law, a French aunt and Spanish nationals in my family,” he says. “I feel intensely not just British and Nigerian, but European. When I tell people this, they say, ‘I understand now why you bang on about it so much.’” Following the referendum, however, he was a voice of caution. “What we were picking up in our constituencies was fatigue with the whole Brexit issue. If you were going to try to steer the country on to a different trajectory, it was not going to be possible in the immediate aftermath. Shouting about something isn’t necessarily going to get you where you need to get to.” He made his case on 5 September 2016, during a House of Commons debate: “I believe that if the deal that is reached at the end of this process is substantially and materially different from that that many of the leave voters believed they were promised, we could legitimately ask for a second referendum, but the fact is that we have not got to that point yet.”

The election shook the kaleidoscope. Umunna immediately proposed an ambitious amendment to the Queen’s speech, demanding the government guarantee Britain’s place in the single market. Though doomed to defeat, it was designed to “flush out the fiction that you can get all the economic benefits of EU membership while outside its economic structures” and jolt the Labour frontbench into breaking with the government. “I got a lot of flak for that amendment, but it brought out into the open the fact that basically we were pegged to the Tory position.” A month later, he and Soubry formed the all-party parliamentary group on EU relations, which includes the Green party co-leader Caroline Lucas and the Liberal Democrat deputy leader Jo Swinson.

That summer, Umunna was approached to take a leading role in coordinating the anti-Brexit forces. “I have to be honest, I was quite hesitant,” he says. But he believed the movement needed unity if it were to succeed. “I said, ‘Look, I want to stop Brexit as much as anyone else, but the question is how?’ My very strong view was that seeking to divide the movement between whether you were pure no-Brexit or soft Brexit was totally unhelpful.”

It’s a bit like a football team. You get a win and the crowd’s on your side again. When we work together, we're stronger

Last autumn, the GCG began to coalesce, formalising months of smaller meetings, conference calls, email chains and collaborations. Simultaneously, the former Tory MEP Edward McMillan-Scott began chairing Where Next for Brexit?, a separate but overlapping talking shop whose heavyweight attendees included Gina Miller, Alastair Campbell, Lord Adonis and AC Grayling. “It got to the point where everyone was saying, ‘Why don’t all these campaigns work together?’” Galsworthy says. “And actually we were – now we just had to communicate that.”

The fantasy of one dynamic saviour to become the face of anti-Brexit had been widely rejected. “It’s just a bit 90s, as if we’ve still got four channels on the telly,” Todd says. “We need different people to speak to different audiences, and the trick is making sure the right ears connect with the right voice.” Malloch-Brown calls it “a two-front fight: the Westminster front is all about day-to-day battles; the country-facing front uses a different set of spokespeople.”

On 13 December, anti-Brexit MPs finally bagged their first victory. Passing by a whisker, amendment 7 to the withdrawal bill required a separate act of parliament to approve the final deal: the crucial “meaningful vote”. Several MPs told McGrory that activists’ letters, surgery visits and social media pressure had influenced their decision. “It’s a bit like a football team,” McGrory says. “You get a win and suddenly the crowd’s on your side again. It was a shot in the arm for two reasons. First, when we work together, we are stronger. Second, this isn’t a done deal.”

***

The ideal scenario for the anti-Brexit movement goes like this. In October or November this year, the government will conclude negotiations and present the final Brexit deal to parliament. Under pressure from their constituents and opinion polls, MPs will vote to reject it and pass legislation for another referendum with a “No Brexit” option on the ballot. Remain will swing enough voters to win the referendum. The government will ask the EU to revoke article 50 before 29 March. RIP Brexit.

Facebook Twitter Pinterest Members of InFacts, Healthier IN the EU, the European Movement, Our Future, Our Choice and Open Britain at their shared offices in Millbank Tower. From left: Rob Davidson, Aurora Lyngstad, Hugo Mann, Hugo Dixon, James MacCleary, Lara Spirit, Alex Clifford and Rachel Franklin. Photograph: Richard Saker for the Guardian

That’s a simple way of describing a fiendishly tricky and unpredictable chain of events. First, success in the Commons depends on Labour both rejecting the deal and supporting another referendum. (“Frankly, if Labour puts its head in the sand and tries to ignore the anti-Brexit effect on our vote in 2017, we will be punished when the next general election comes,” Umunna says.) The next hurdle is passing legislation for a referendum, which would normally take a year. Then the anti-Brexit cause would need to win that referendum. The latest polling by YouGov and ICM gives remain a slim lead, but ComRes and ORB favour leave. Finally, it’s unclear whether the EU27 would be sympathetic to an 11th-hour change of heart. “We could be in a level of constitutional uncertainty I’ve never seen in politics,” McGrory says. “To try to game-theory this is really hard.” He’s a realistic optimist. “Well, you’d like longer, wouldn’t you? It’s by no means unachievable, but it’s unquestionably a stiff task.”

Preparations have escalated dramatically. In the first week of March, eight key groups moved into shared offices at Millbank Tower – on the same floor, coincidentally, as the website brexitcentral.com. When I visit a week later, the main office still has an ad hoc feel, with nothing on the three banks of desks apart from laptops, papers and a communal bowl of sweets. Each organisation’s sector of the office is marked by a colourful banner or cardboard display.

Open Britain has the largest following – 550,000 email subscribers and 553,000 Facebook followers – and the strongest connections with the media and MPs; Lord Mandelson is a founding board member. Britain for Europe and the European Movement maintain branches around the country, keeping the conversation alive and preparing to spring into action the moment a referendum is announced. Scientists For EU and Healthier IN the EU are maestros of social media. InFacts is an unrivalled data resource. The wittily acronymed Our Future, Our Choice (Ofoc) and For our Future’s Sake (FFS) speak to younger voters. Meanwhile, Best for Britain, which maintains separate offices, uses its war chest to fund polling, advertising and regional “barnstorms”, inspired by Barack Obama’s campaigns, that teach activists how to get out of their echo chambers and talk to wavering leavers. Between them, they cover the waterfront.

Facebook Twitter Pinterest Femi Oluwole of Our Future, Our Choice: ‘The will of the people has an expiration date.’ Photograph: Mike Pinches/The Guardian

“We need ruthless pragmatism,” says Dr Rob Davidson, who co-founded Scientists for EU and Healthier IN the EU with Galsworthy. “No group is big enough on its own. We’ve all tried working with different combinations of people. There have been fallings out, there have been splits. What we’ve found here is people who are willing to be pragmatic.”

The Millbank move was a precursor to the launch of the People’s Vote on 15 April – the campaign seeks to establish the democratic legitimacy of a vote on the deal. “It’s the most significant thing that’s happened on our side of the argument since the referendum,” McGrory says. “It’s what everyone’s wanted for ages. Why don’t you have a single campaign with a very clear ask? Well, there is one now.”

A recent YouGov poll found that only 38% of voters backed a vote (the unpopular term “second referendum” is verboten), with 45% opposed, although the gap is narrowing. “It feels like a Jedi mind trick has gripped the country, like ‘the will of the people’ was only 23 June,” Todd sighs. “It’s important for us to normalise debate and make people feel like it’s OK to say, ‘You know what, I don’t think this Brexit thing is going that well. Maybe we should look at it again.’”

One argument is that there was no form of Brexit on the ballot paper and that campaign promises have been broken. “When will we know what we voted for?” asked Best for Britain’s recent billboards. Another argument is demographic: there are already half a million new voters since June 2016, and multiple studies predict the British electorate will be firmly pro-remain by 2021. “The will of the people has an expiration date,” Ofoc’s co-founder Femi Oluwole says.

James MacCleary, the campaign director for the 69-year-old pressure group European Movement UK, thinks the campaign would be fought over “quite a small section of persuadables: probably 10%. We’re trying to identify the motivations, values and identity politics of people in that available group, and find ways to address issues they’re concerned about.”

The pro-EU cause seems to be shifting into the right corner of Malloch-Brown’s diagram. Umunna calls it a role reversal, with the leavers now in government and the remainers the fleet-footed rebels. “We think Brexit is being driven by elites,” says Tom Brufatto, chair of Britain for Europe. “Nigel Farage is a career politician – a failed one, but still a career politician. Arron Banks is a multimillionaire. They’re just a different type of establishment. We see an opportunity to brand ourselves as the change campaign that provides real solutions to the factors that led to Brexit.”

The challenge is formidable, but morale, support and fundraising are at their highest since the referendum, with even Farage admitting “the remain side are making all the running”.

***

It’s a bright, chilly March morning in Leeds. Thousands of people have gathered outside the Art Gallery for the Great Northern March, one of several simultaneous Stop Brexit protests designed to show that opposition is growing around the country. Drums are pounded, flags are waved, placards are held high, among them one that reads “Stop pretending this is a good idea!”

Facebook Twitter Pinterest Inside the Best for Britain offices. Photograph: Suki Dhanda for the Guardian

Eloise Todd scrutinises the expressions on bystanders’ faces to see if the issue is resonating with the public. At Best for Britain’s barnstorms, activists are sternly told that things that galvanise remainers, such as flags and Bollocks to Brexit stickers, are counterproductive when it comes to swaying the unconverted. A middle-aged man comes over to lend his support. “An enthusiastic northerner!” Todd says. They exchange a few words. “Oh,” she says. “He’s Dutch.”

The march concludes with a rally. Brufatto is here, as is Oluwole, whose bright red T-shirt reads: “I’m Femi, talk to me about Brexit.” “The mood is hopeful,” he says. “We’re out on the streets saying that you’re not alone if you think this is a disaster and you want things to change.”

Alongside marquee names such as Adonis and Grayling, the speakers include a Labour MEP, a Lib Dem peer, a former Tory councillor, a union official, a Spanish-born nurse and an Ofoc member who regrets voting leave. The voices are diverse, but they all hit the same notes: new facts have emerged; the negotiations aren’t delivering what was promised; a people’s vote is a democratic necessity; Brexit is not inevitable. Three weeks later, they will announce the People’s Vote.

“The people of this country are not daft,” Todd says from the stage. “Especially not in Yorkshire.” She raises her voice for a final rallying cry, triggering a cascade of cheers and applause. “Let’s do it!” But Todd knows that rallying the base is the easy part. The real fight is just beginning.

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