At 8am each morning, in an unassuming office in Finsbury Park, north London, members of one of the most feared — and admired — political organisations assemble. Inside Momentum’s new headquarters, where some staffers remain 12 hours later, the mood is one of defiant optimism. “Days till socialism: 37” reads a handwritten sign on the wall, charting the advance towards the electoral nirvana promised on 12 December.

When Momentum was founded in October 2015, a month after Jeremy Corbyn’s election as Labour leader, the activist group was dismissed by many politicians and commentators. Tom Watson, the party’s outgoing deputy leader, described it as “a rabble ... I just don’t think they’re that effective”. Others likened it to the Militant Tendency, the Trotskyist sect that Labour expelled from its ranks in the 1980s, or a cultish Corbyn fanclub.

But the 2017 general election forced the political establishment to start taking Momentum seriously. By deploying digital innovations, such as the app My Nearest Marginal, and ambitiously targeting Conservative seats that had been deemed unwinnable — Canterbury, Kensington and Portsmouth South — the group helped Labour deprive Theresa May of her parliamentary majority. Its slick and accessible videos, such as “Daddy, do you hate me?”, which showed an imaginary conversation between a Tory-supporting father and his young daughter, were watched by 12.7 million unique Facebook users users (more than one in three in the UK). On the day of the election, 10,000 Momentum activists knocked on an estimated 1.2 million doors in the UK.

“This isn’t the band that’s playing in the garage any more, this is a band that can book a serious venue,” Laura Parker, Momentum’s national coordinator, told me. After the 2017 election, former Conservative communications director Giles Kenningham lamented that Momentum’s interventions had a “devastating effect”. The Tories, he observed, “did not have an equivalent campaigning group pushing out their message”.

Indeed, when a young Conservative activist unfavourably compared his party’s campaign with Labour’s, Michael Gove replied: “A few months ago people would have thought of Momentum as a group of people who were completely ideological, who were being manipulated by [Momentum chair] Jon Lansman and various others, and who were a threat to democracy.”

Now, he continued, “I think people will change their view ... that actually Momentum brought lots of enthusiastic young people into politics, provided them with an opportunity to campaign for things in which they believed and that it also helped change the culture of the Labour Party ... I do think we can learn something from them.”

Gove’s comments are perhaps less surprising than they appear. The Conservative cabinet minister, who kept posters of Lenin and Malcolm X on his wall as education secretary, and who has cited the Italian Marxist theorist Antonio Gramsci, has long understood that politics is not merely a struggle for seats but for intellectual and cultural hegemony.

As well as a “war of manoeuvre” — direct conflict between political forces — Momentum wages what Gramsci called a “war of position”: a long struggle on the terrain of civil society with the aim of changing what the philosopher called “common sense” (or the “philosophy of non-philosophers”).

Through the annual The World Transformed festival at the Labour Party conference, and spin-off events (Bristol Transformed, Birmingham Transformed, Nottingham Transformed), Momentum has resurrected dormant concepts such as political education and municipal socialism, pioneered new ones such as “acid Corbynism” (an adaptation of the late Mark Fisher’s “acid communism”) and intersected with movements from Extinction Rebellion to grime.

“We’ve got to convert ordinary members and supporters into real cadres who understand and analyse society and who are continually building the ideas,” John McDonnell, one of the Labour politicians closest to Momentum, remarked in 2018.

Oscar Wilde may have quipped that the problem with socialism “is that it takes up too many spare evenings”. But in the era of Momentum, for an ever greater number of activists, the risk is rather that spare evenings may distract from socialism.

***

In late October, as Labour prevaricated over whether to support an early general election, Momentum was unambiguous. “We say: bring it on,” declared an email to the group’s 40,000 members (an increase of 16,000 since the last election). “Our movement is stronger than ever. We defied all expectations at the last election. If tens of thousands of us step up and give it everything we’ve got — we can win.”

The results since partly justify such bullishness. Within 12 hours of the general election being called on 29 October, the group had raised £100,000, with an average donation of £24.40. At the time of writing it had received £450,000, easily surpassing its 2017 total of £260,000.

Momentum has launched a new app, My Campaign Map (described as “My Nearest Marginal on steroids”), which uses data-driven metrics to continually update members on where they can make the greatest difference. After its triumphs in 2017, the group is this time seeking to unseat Conservative including Iain Duncan Smith in Chingford (majority: 2,438), where 700 activists campaigned one recent weekend, and Boris Johnson himself in Uxbridge (majority: 5,034, the smallest of any prime minister since Ramsay MacDonald in 1924).

A new programme, Labour Legends, has challenged would-be Stakhanovites to devote a week or more to full-time campaigning (1,400 have signed up). On 30 October, Momentum held what was reputedly “the largest mobilising call in UK history”, with more than 2,000 participants.

“Be up for it, it’s going to be cold, it’s going to be wet, the weather will not be great, I promise you,” Corbyn told them. “But you’ll look back on the winter of 2019 as the time you delivered a government that didn’t believe in free-market economics and neoliberal thoughts, instead believed in people, believed in social justice, whose whole being is based on our socialist values and you will have got cold and wet for a very good reason.”

Momentum’s paid staff of 55, which has grown from 15 in 2017, is supported by a network of “distributed organisers”, a campaigning model inspired by Democratic presidential candidate Bernie Sanders. Rather than treating volunteers as cannon fodder for door-knocking, this decentralised strategy sees them engaged in fundraising, recruitment and social media output. Throughout the day, Momentum activists scour the UK’s news channels, poised to “clip” successful Labour interviews, or calamitous Conservatives ones, and upload them to the group’s shared drive.

“The social media operation is vastly bigger than we had last time,” Jon Lansman, Momentum’s chair and one of its founders, told me when we met recently at the group’s HQ. “We’ve already had 20 million views, seven over a million, one got three million [“Tories caught making stuff up”]. Our viewing figures are better than any of the other political social media operations.”

Lansman, who also sits on Labour’s National Executive Committee (Momentum-backed candidates won eight of the nine elected places in 2018), provided one of the most memorable moments of any party conference when he tried and failed to abolish the post of deputy leader. Has he spoken to Tom Watson since? (“It’s the hit man that missed,” jeered Watson at Lansman during the conference.)

“I have spoken to him,” revealed Lansman. “He was very generous and warm at the last NEC meeting. He thanked me for supporting his candidacy [in West Bromwich East] before he decided to pull out ... It got a good laugh.”

The Momentum head still favours the abolition of the deputy post. “I think an elected general secretary would be more worth having than an elected deputy leader,” he said. “We’ve got a vacancy coming up, I wouldn’t advocate filling it. I would prefer to delete the post.”

He also revealed to me that he would campaign for Remain in a second Brexit referendum (“I think it’s right that we went with a choice between a sensible deal and Remain even though I personally would campaign for Remain”) and that he still favours the introduction of open selections, or mandatory reselection, allowing candidates to stand automatically against incumbent MPs (“It would be far better to have a positive choice between candidates rather than voting for or against a candidate, the incumbent”).

Lansman, 62, first came to public prominence as the co-ordinator of Tony Benn’s 1981 deputy leadership campaign. “To be less than 1 per cent below Denis Healey is a terrific result,” he told ITN minutes after Benn’s defeat. “The campaign for the policies and the campaign for party democracy will go on — and there’s nothing that’s going to be stopping it.”

The campaign went on but Lansman and the left entered what he calls “the wilderness”. In the 1988 leadership election, Benn suffered a landslide defeat to Neil Kinnock (89-11 per cent) and the party moved rightwards. For decades, Lansman was a figure on Labour’s fringes, known only to super-activists and party obsessives. And then Jeremy Corbyn was elected leader, allowing the left to escape the “sealed tomb” that Peter Mandelson had intended for them.

Lansman, immediately recognisable from his psychedelic shirts and omnipresent backpack, is now more influential than at any other point in his long career. I asked him how Benn, Corbyn’s political mentor, would have viewed Labour’s 2019 manifesto. “I think Tony would have been delighted to see a manifesto which I think exceeds the scale of the ambition of the two Labour Party programmes that he devised as chair of the home policy of the NEC in the 1970s.

“They were the last statements of a serious transformative alternative economic strategy that the party has produced. This is actually much more complete, much bolder. It’s got, of course, the additional dimension of the transformation that is required to deal with the climate emergency and it rises to that too.”

Yet the manifesto is not without critics. Some members were dismayed that motions passed by activists at last year’s Labour conference, such as one supporting the maintenance and the extension of free movement, were not reflected in the document (Corbyn has taken to promising that there will be “a lot of movement”).

Laura Parker, 49, who became Momentum’s national coordinator in November 2017 having served as Corbyn’s private secretary, is one of the left’s foremost pro-Europeans and a champion of migrant rights. She lived and worked in Bulgaria, Romania, Belgium and Italy for 17 years (including for Save the Children and the EU Commission) having been born in Leeds, and speaks French, Spanish, Romanian, Bulgarian, and Brazilian Portuguese. As a beneficiary of free movement, Parker feels a moral imperative to defend this right for others.

Was she disappointed that the manifesto did not echo this stance? Parker paused for 20 seconds, torn between her political professionalism and her personal loyalties.

“I think when you look at where we were, the party’s made a significant shift,” she eventually replied. “The 2019 Labour Party is not going to produce a mug which asks for controls on immigration [as the party did under Ed Miliband in 2015], there’s a commitment to closing detention centres, commitments to voting rights for residents, so that EU citizens can vote. There’s been a very purposeful attempt to kill the myth that it’s migrants who drive down wages. I think we’re in a much better place than we were.”

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Labour’s policy divisions are far outweighed by the fraught matter of anti-Semitism. As a 16-year-old, the Jewish Lansman worked on an Israeli kibbutz. “It was actually a very politicising experience,” he later recalled. “When I did my bar mitzvah I saw myself as a Zionist and I think after I went there I felt it less. I was more interested in the kibbutz and what I liked about it was the pioneering spirit, the sense of community and radicalism of it.”

I asked Lansman, who has previously criticised Labour’s handling of anti-Semitism, whether he believed the party was still falling short. “I think we have greatly improved the process for dealing with all forms of complaints, not just anti-Semitism but sexual harassment and others,” he replied.

“There are other forms of racism and hatred, by the way, in the party and a lot of the cases of anti-Semitism that I see, and I see most of them because I sit on most of the anti-Semitism panels, also involve other forms of hatred. We have people who as well as being Holocaust deniers, people who hold all Jews responsible for all actions of the Israeli government, we have examples of Islamophobia, anti-Hindu hatred, homophobia and misogyny.”

He continued: “There is prejudice in all of us, the most important thing is to make people aware of their unconscious biases, aware of prejudices and work to eliminate them through education.”

Does it trouble and upset him that so many Jews are urging non-Jews to reject Labour? “Yes, of course it upsets me. I don’t think it’s right, by the way, I tweeted the other day about what I thought was an extremely good, well put-together piece against the charges of anti-Semitism against Jeremy.

“But it does upset me that people have the views that they do. I think we genuinely are dealing with the issue, there’s more to be done, there’s more education to be done ... But we are not going to have the support of many people in the Jewish community, who I hope in due course we can win back.”

Partly owing to the damage that charges of anti-Semitism have done to his reputation, Corbyn entered the general election with the lowest personal ratings (-60 in an Ipsos MORI survey) of any opposition leader in polling history (his ratings have since modestly improved). Is the problem for Labour, as some suggest, that its policies are popular but its leader is not?

“Well, they could be better,” Lansman conceded of Corbyn’s ratings. “I think that was true in 2017 as well ... With the broadcasting regulations kicking in, I think once again people will see that the real Jeremy Corbyn isn’t quite the same as many of our tabloid newspapers present him. I think we can overcome that too.”

Momentum’s training sessions in “persuasive conversations” are aimed at achieving precisely this. Rather than reciting monotonous scripts, activists are encouraged to meaningfully engage with voters. At one such session I attended on 21 November, held at Unite’s London office in Clerkenwell, Aydin Dikerdem, a charismatic young community organiser, invited activists to “start shouting out the things that you’re worried about coming up”.

The answers were swift: “Anti-Semitism, tactical voting for the Lib Dems in Tory areas, magic money tree, IRA, racism, position on Brexit, going backwards to the 1970s, high taxes, Momentum, people hate, people don’t like Momentum. Immigration, Corbyn not being a leader, economic impact of a four-day week.”

Dikerdem, who was elected in 2016 as a Labour councillor in Wandsworth (the original laboratory of Thatcherism), explained: “There was a lot of controversy when we decided to do this because we’re going to talk about some things that are really controversial but we thought it was really important.

“What if someone brings something uncomfortable up? What if someone asks me something really tough? I’m not equipped to answer difficult questions on Corbyn and anti-Semitism. And we wanted to address that elephant in the room because if there are elephants, if people go in with baggage and they’re feeling uncomfortable you’re not going to build trust because there’s going to be nervousness.”

Successful political movements identify their vulnerabilities and work ruthlessly to neutralise them. But that Momentum activists can readily name so many perhaps augurs less well.

***

After Labour’s landslide election victory in 1997, supporters asked each other “were you up for Portillo?” The defeat of the Conservative cabinet minister in the safe Tory seat of Enfield Southgate (majority: 15,563) was the evening’s coup de grâce.

In June 2017, after four recounts, a comparable moment of elation occurred when Kensington turned red. Since its creation in 1974, the UK’s wealthiest constituency had been the sole property of the Conservative Party (Portillo himself represented the seat from 1999-2005). On election night, as the scale of the Tories’ humbling became clear , Rachel Johnson, the sister of Boris Johnson, trembled like a French aristocrat confronted by insurgent Jacobins. It gave her “shivers,” she told CNN, to think that “the home of Kensington Palace, Peter Pan, Diana, Princess of Wales’s old house” may have fallen to the Corbynites.

On the evening of 12 November, hundreds of Momentum activists assembled in Tavistock Square with the intention of keeping Kensington red. “You know what happened last time? It was a shock to us all, especially me, it messed my life up slightly,” Labour candidate Emma Dent Coad, 65, a Corbynite republican whose political hero is Tony Benn, told the crowd.

“A lot of people round here remember where they were. They were in the pub and everyone screamed, truly ... We overturned a Tory majority of 7,000 for me to win by 20.”

The slightness of Dent Coad’s majority (the third-smallest in the UK) leaves no room for error. But on the doorstep the reception is ambiguous. One traditional Labour voter deems Dent Coad too “eccentric” for his taste. A young woman is leaning towards the Liberal Democrats but is persuaded to reconsider after discovering, to her surprise, that Labour supports a second Brexit referendum.

Four days later, a new Kensington survey by Deltapoll showed Labour in third place on just 27 per cent (down 16 points), behind the Liberal Democrats, represented by former Conservative minister Sam Gyimah, on 33 per cent and the Conservatives on 36 per cent. Dent Coad, the seat’s first Labour MP, would become the first party candidate to finish third.

But Momentum is invariably stoical in the face of such polling, mindful that the Conservatives’ average poll lead before the 2017 election was 8.5 points (they ultimately finished just two ahead of Labour). “Nearly every pollster predicted a Tory landslide,” an email from Parker to members noted the day after an Opinium survey put Labour 19 points behind the Conservatives. “They had us down by up to 13 points — and a day later we proved every single one of them wrong.”

More recent polling by BMG Research has shown Labour narrowing the Conservatives’ lead to just six points. In her 1989 Conservative conference speech, Margaret Thatcher declared of the newly-founded Liberal Democrats: “They have never learned what every woman knows — you can't make a soufflé rise twice.” Momentum’s wager is that you can.

Momentum was founded with the intention not just of guarding Corbyn’s leadership in its infancy but of cementing the left’s supremacy. Four years after the group’s creation, its leaders are determined that it will outlast him.

“This goes way beyond bodyguarding and way beyond Corbyn,” Parker said. “I want him to win this election and I want him to be the prime minister. But only somebody very, very foolish or completely disingenuous would suggest that the radical agenda for change we’ve got is going to be delivered in one term. Long may he live and long may he feel like being prime minister, but at some point Jeremy is going to go to his allotment and this project is going to go on beyond that.”

In private, there is already live debate among Momentum activists over whether Corbyn’s successor should be a “true believer” such as shadow business secretary Rebecca Long-Bailey or shadow employment rights secretary Laura Pidcock, or a more experienced figure such as shadow Brexit secretary Keir Starmer or shadow foreign secretary Emily Thornberry. Provided the latter pass the left’s litmus test, some say, they could yet pursue “Corbynism without Corbyn”.

Neither Parker, nor Lansman, would name a potential successor. Instead both emphasised, as Benn would often do, that it was the issues, not the personalities, that mattered.

“I don’t care who the leader is as much as I care about the fact that they do not reverse the changes that we’ve made in the party, said Parker. “I want the economic agenda of John McDonnell, the commitment to human rights, the commitment to peace, I never want another Labour leader again who will take us into an illegal war, I never want to hear any key Labour advisers say ever again that they’re intensely relaxed about the filthy rich.”

“Momentum is a permanent feature of the Labour Party,” Lansman said. “We’re not going to be marginalised again, we’ve got half a million members and they are committed to the transformative programme we’ve got. We haven’t just got the programme that Jeremy wanted, we’ve got the programme that those half a million members wanted. There’s no going back to austerity, there’s no going back from a significant role for the state in accepting responsibility for the well-being of communities and for the success of the economy in delivering decent incomes and job security.

“We are going to be here long after Jeremy Corbyn and I are both dead.”