Few, if anyone, gave Jeremy Corbyn much chance when he scraped on to the list of Labour leadership candidates in June. Not the MPs backing him. Not the media. Not the bookies. Not even his own small campaign team.



One of the key figures in that team, Kat Fletcher, did go into a betting shop in London’s Holloway Road to put £20 on him early on. The odds were 100-1.



In spite of that bet, Fletcher, the deputy mayor of Islington in London, admitted this week she did not place it with any sense of confidence. “To be honest, the bet was an act of solidarity,” she said. “It was so I could tell Jeremy that I had backed him.”

Corbyn has defied not only Fletcher’s expectations but everyone else’s. He has come from the fringes of Labour politics, where people still proudly describe themselves as socialists and refer to one another as comrade, to lead one of the biggest grassroots political uprisings in the UK in recent times, a movement that has taken him to the verge of becoming party leader.

The journey began in the early summer when a small group of Labour leftwing MPs gathered at Westminster to decide who should stand. It was a doomed mission as far as they were concerned but someone had to do it, to be the voice of the left, alternative candidate in the contest. It was decided it was Corbyn’s turn to be the sacrificial lamb.

Jeremy Corbyn leaves his home in north London on Friday. Photograph: Stefan Wermuth/Reuters

The initial problem was getting him on the ballot, which required the backing of 35 MPs and he only had 22. He found the necessary nominees just before the midday deadline on 15 June, some MPs doing it as a gesture of goodwill to allow a broad debate, others after coming under pressure from a social media campaign.



Former foreign secretary Margaret Beckett, who was among those who agreed to nominate him, later expressed regret as his campaign gained momentum, describing herself as a “moron” for having done so. Asked about this, one of Corbyn’s campaign team, MP Richard Burgon, said this week “moron? That is impressively self-critical. I do not think she is a moron. I think members will be grateful to her for doing the right thing.”

Having got on the ballot, he built a small campaign team of about 20 people. The key players included: fellow Labour MP and friend, John McDonnell; Simon Fletcher, who worked for Ken Livingstone and Ed Miliband; Kat Fletcher (no relation to Simon), former president of the National Union of Students; and Carmel Nolan, a former radio producer from Liverpool.

Jeremy Corbyn surprised by support during Labour leadership campaign Guardian

Among the new generation of MPs backing him was Burgon, a trade union lawyer and former chair of the Cambridge university Labour club, and Clive Lewis, a former BBC reporter and infantry officer who on election night had declared New Labour to be dead and buried.



The campaign has from the start had a casual feel to it. When Nolan was interviewed for the job as head of media, she was interviewed on a park bench beside parliament, with Simon Fletcher sitting beside her and McDonnell on the ground.



The whole campaign has been the antithesis of the political model that has become standard over the last 30 years, exemplified by Peter Mandelson and Alastair Campbell in the Blair years, with their focus groups, tight messaging, choreographed stage appearances, instant rebuttal units and speeches timed to coincide with BBC peak news bulletins.



Corbyn speaking to journalists outside the Commons after the historic ruling by the House of Lords against the appeal of former Chilean dictator Augusto Pinochet in 1998. Photograph: Fiona Hanson/PA

Corbyn’s speeches by contrast were not meticulously organised to coincide with the BBC’s Six O’Clock News or Ten O’Clock News. His rallies usually started around 6.30pm or 7pm so he could get a train back to London the same night whenever possible.

The campaign team, which was based at the headquarters of the transport union TSSA near Euston and the Unite headquarters in Holborn, both in London, began packing up on Thursday when balloting closed.



They have different memories of the moment they realised Corbyn was more than a no-hope candidate. For each of them, it was when they first became aware of big crowds turning up at rallies. For Nolan, it was a rally on Merseyside, at Birkenhead town hall, on 9 July, when 350 people turned up. A clipboard was sent round to gather names: 100 signed on to work phone banks canvassing potential supporters and 50 said they planned to join the party. Three weeks later, 1,500 crammed into the Adelphi Hotel in Liverpool.

Coupled with this groundswell of popular support was the backing of the unions early in July. It could all have been very different if Andy Burnham had initially embraced the unions. Unite and other unions had been flirting with Burnham as the left alternative to Yvette Cooper and Liz Kendall. But, apparently fearful of being portrayed as the leftwing candidate, he spurned their offers of support and they turned instead to Corbyn.

Asked by the Guardian if Burnham had made a serious miscalculation, Len McCluskey, Unite’s general secretary, who was at Corbyn’s 99th and final rally on Thursday night, said: “Well you have to ask Andy that question. The reality is he probably made a mistake because he did not seize the moment to run as an alternative.”

When Kat Fletcher joined the campaign team just after Corbyn was nominated, she was put in charge of coordinating volunteers. It is not easy finding people prepared to give up time to sit on phone banks contacting potential voters. But Fletcher quickly found herself inundated with offers of help. By the end of the campaign, Corbyn had attracted an extraordinary 16,241 volunteers.

Corbyn speaks to over 1,200 supporters outside Great St Mary’s church in Cambridge last week. Photograph: Rob Stothard/Getty Images

The biggest concentration of volunteers were in London, with 3,832, followed by 1,170 in the south-east of England and 1,160 in the north-west of England. There is no breakdown in terms of age, but, according to Fletcher, the youngest person on the phone banks was 13 and the oldest 92.

Cited as an example of the effectiveness of grassroots movements, the Corbyn team points to one of the volunteers who designed a new tool, a canvassing app, which allows anyone in the country to set up a phone bank on their home computer – making calls, listing questions to be asked and providing a place for answers to be registered. Fletcher thinks it will become widely adopted.

Social media played a big part in volunteer recruitment. David Heywood, a long-time Labour member who resigned over the 2003 Iraq invasion and rejoined in 2010 when Miliband became leader, became involved after exchanges with political friends on Facebook. He and about a dozen others turned up at a phone bank in the offices of Unite in Norwich.

Corbyn’s vote against the welfare bill on 20 July, in contrast to Burnham, Cooper and Kendall, who all abstained, is often cited as a pivotal moment. But Heywood does not agree. “I think the decision to abstain on the welfare bill angered many people – they just could not understand the logic – but I don’t think it was the most significant factor.” What attracted Heywood was Corbyn’s personality: calm, measured, he does not get riled and “speaks like a real person”.

Corbyn with other candidates Yvette Cooper, Liz Kendall, and Andy Burnham at the end of the Labour party leadership final debate at the Sage in Gateshead, 3 September. Photograph: Scott Heppell/AP

For Burgon, MP for East Leeds, the attraction of Corbyn was that he has clear, alternative policies “so that I would never again have to stand on the doorsteps and hear people saying ‘you are all the same’.”

The Corbyn strategy has been fairly simple: do not make personal attacks on the other candidates, do not go negative and instead stick to outlining policy plans. He bypassed much of the mainstream media, which at the beginning tended to be sneering. Television and radio, which initially largely ignored him, has in recent weeks been flooding his campaign team with interview requests: the BBC Today programme has been sending almost daily requests for Corbyn to go into the studio.

His team point to the odd supportive piece early in the campaign in the New Statesman, Independent and the Guardian, along with the Morning Star, Labour List and the Huffington Post, but much of the rest of the coverage has remained unremittingly hostile. The campaign team ignored most of it, though it did lodge a complaint this week with the BBC’s head of news, James Harding, over Monday’s Panorama profile.

There is a dread at Westminster among some Labour MPs, officials and advisers from the centre and right of the party. Some of them cling to the hope that Corbyn privately sees himself as a stop-gap leader, ready to hand over to someone else before the 2020 election. Corbyn does not see it that way: he has changed during the campaign, emboldened by the support, and is in for the long haul.



The bookies have not waited for the announcement of the results of the ballot and have already paid out. Fletcher has picked up her £2,000 winnings and is using it to pay for accommodation for about 20 campaign ‘super-volunteers’ – those working almost daily – to attend the party’s annual conference at the end of the month in Brighton, in the hall to hear the new leader deliver the keynote speech.