Jeremy Corbyn wasn’t at home when the 10pm exit poll came in. Amid tight secrecy and security, the Labour leader was instead ensconced in a ‘social enterprise hub space’ in his Islington constituency.

Watching the news on a big TV screen alongside wife Laura and three sons Ben, Seb and Tommy, the instant reaction was one of raw shock.

Coffee-drinker Corbyn avoids caffeine at night time and relies instead on fruit juice to keep him hydrated for overnight counts. But it was the political squash of this historically catastrophic Labour election result that left a sour taste in the mouth for him and his tight-knit team of staffers.

Across London, up on the second floor of the party’s HQ in Victoria, more than 100 bottles of specially-designed ‘Corbynista Victory Ale’ were left unopened as a planned celebration for staff was suddenly abandoned. “The place cleared about 45 minutes after the exit poll,” one insider said. Up on the building’s 8th floor, senior staff frantically planned the ‘lines-to-take’, stating: “The defeat is overwhelmingly down to one issue — the divisions in the country over Brexit.”

After the avalanche of seats fell to the Conservatives, Corbyn headed off in the Islington rain to his own constituency count at the Sobell Centre. In a bitter irony on this night of a Brexit landslide, the venue was the place where prime minister Harold Wilson held a special Labour party conference on Europe policy in 1975. Back then, its working class trade unions voted to leave the ‘Common Market’, but the party went on to approve a Yes vote in that year’s referendum.

Just after 3.20am, Corbyn delivered his defiant speech, refusing to apologise for his or his party’s failures. Instead he attacked media intrusion on his family life and stuck to the pre-prepared script sent to all MPs that this was a “very disappointing night”, before confirming he would step down after a period of ‘reflection’.

One Labour MP watching the performance texted a colleague a string of expletives that ended with: “He’s in total f*cking denial.” Ed Miliband’s former speechwriter Marc Stears said: “Corbyn is entirely incapable of reflection. He should show dignity and go straight away.” After his speech, Corbyn received a brief hug from fellow Islington MP Emily Thornberry, before heading off home.

Yet the results really weren’t a shock to many people in Labour’s high command. Several weeks ago, as Boris Johnson was pushing hard for a general election, Jeremy Corbyn’s aides were getting irritated. The cause was not the PM’s bluster or arrogance, it was a huge, third party polling survey that had been circulating within the higher reaches of the party. HuffPost has learned that the data showed a jaw-dropping figure: Labour was on course to get fewer than 200 seats in an election.

Rather than pausing to think the poll could be close to reality, the reaction of the Labour leader’s team was to lash out at those who had presented it. Even though the party’s own internal polling had been coming up with similarly apocalyptic warnings months before, Team Corbyn were convinced they could pull off the same trick of 2017 and use a campaign to narrow the Tory lead.

Shrugging off pleas from MPs to hold off any election until 2020, possibly after Johnson had passed his Brexit deal, the leadership went ahead with a plan to agree to a winter election. With Jo Swinson and the SNP vying with each other to look like the party most vociferously demanding an election, Corbyn decided he could not stay quiet any longer. The die was cast for the biggest defeat in nearly 100 years.

Even before the election was called, internal divisions were bubbling under the surface. Shadow minister Jon Trickett wanted Corbyn to make clear before the party conference that he would stay ‘neutral’ in any future referendum. But in the end a decision was taken to pivot to the new stance in the middle of the campaign, during a BBC Question Time. The new position was swiftly condemned by both Leavers and Remainers in the party as too little too late.

Some allies of shadow chancellor John McDonnell felt frustrated too that the leadership was ignoring a chance to push a wider agenda of answering Leave voters’ demands to ‘take back control’ of their lives. McDonnell did finally road test his slogan that Labour would “put money in your pocket and power in your hands” – but not until three days before polling day.

One big problem was the sheer size of the manifesto and the number of policies on offer. Candidates complained that they didn’t have a single five-point pledge card like the one Tony Blair made famous. While the Tories had a simple message of ‘Get Brexit Done’, Labour lacked a similarly easy ‘doorstep offer’. “We had so much in the manifesto we almost had too much,” one senior source said. “It felt like none of it was cutting through. You needed to boil it down.”

“We tried to give a retail offer and also a grand vision and ended up falling between the two stools. To get across ‘you’ll be better off with Labour’, we should have made our position clearer much earlier.”

Corbyn’s chief of staff Karie Murphy, who was shifted to party HQ for the campaign, caused fresh friction in her new role. “She got more power than she ever dreamed of,” one party official said. Murphy effectively took control of the party’s parliamentary selections process, to get Corbyn allies and Momentum-backed contenders in plum seats.

Her pet project had already been a national network of ‘community organisers’, who were meant to target activism in de-industrialised towns like Mansfield across the midlands and north. Critics saw the organisers as Murphy’s attempt to bypass and undermine regional officials who were seen as too close to the Blair, Brown and Miliband eras.

Some organisers were even handed key constituency selections. But the experiment not only failed to help save Labour seats, it cost an estimated £3 million of badly-needed funds. “We’ve got literally no idea what these people did,” one MP confided.

On Friday, general secretary Jennie Formby – another key Corbynite who worked closely with Murphy – wrote to all staff to warn them that the party may lose their jobs at the end of the year because of the loss of Labour MPs will reduce public funding known as ‘Short Money’. Critics said that the letter underlined how cash-strapped the party really was.

Another key Corbyn aide, communications and strategy chief Seumas Milne, was tight lipped as he accompanied his boss to Islington Town Hall at lunchtime. Corbyn recorded a TV clip (dubbed a ‘hostage video’ by one insider) which hinted that he may quit “in the early part of next year.” “I will stay here until somebody is elected to succeed me,” he said. One party source said: “Seumas and Karie are holding Jeremy hostage in the job while they figure it out.”

Some Corbyn supporters want him to stay on for several months and get a new leader and deputy leader in place in time for May’s Metro Mayor and local elections. But the race for the succession had already begun in the early hours as Lisa Nandy, Rebecca Long-Bailey and Jess Phillips all refused to rule out running for the top job.

Nandy, who has pushed a ‘small towns’ policy agenda for years and urged respect for the Leave vote, made a speech at her count in Wigan that was swiftly clipped and shared on Whatsapp groups. “To every single one of those voters who want to put their cross in that box for Labour, I have listened and I have heard you. And I will make it my mission from this day forward, to bring Labour home to you,” she said.

By Friday morning, David Lammy – namechecked by Nandy amid suspicions they may run on a joint ticket – and Keir Starmer were clearly also in the frame. Starmer, dressed in a casual jumper rather than his usual suit, told a TV crew “I don’t underestimate the size of the task ahead”. He has already been building a team around him and many noticed a leadership-style Instagram post last week. By contrast, Emily Thornberry has been mysteriously quiet.

Angela Rayner, seen by some in the party as the best hope of reconnecting with working class voters, also stayed away from the cameras. Some who know Rayner well believe she is too protective of her young family to risk running, but others suggest she is seriously considering the job and her union Unison has a formidable machine ready and waiting to back any leadership bid.

“Angie’s had a good election,” said one senior party figure impressed by her combative performances in two TV debates in the past week. “She has that capacity to speak to people in a warm way. Education is a big issue for members and she’s in a strong position.”

Long-Bailey, dubbed “Becky Wrong Daily” by fellow MPs unimpressed by her closeness to McDonnell, is seen by many as a favourite if she can win big union backing. She earned plaudits for her own performance in one election debate and raised eyebrows with a ‘backstory’ video of her own in the election campaign. “A northern woman leader could at least start us on the long road back,” one MP said.

Either Long-Bailey or Rayner could win the support of Momentum, seen as important in any member-led election. Yet the sticking point is that the pair are incredibly close friends and flatmates in London. They went on holiday together in the Lake District this summer, sharing a tent with their children.

Many believe they would never stand against each other, and are waiting to see which one declares first. It’s possible that one could stand for leader and the other for deputy leader, a post already vacated by Tom Watson.

HuffPost last week asked Rayner if there was a possible ‘Granita pact’ on the future leadership (Gordon Brown agreed to step aside for Tony Blair over lunch in an Islington restaurant in the 1990s). She replied: “Well, to be honest, we don’t even talk about it. We are just too knackered doing our day job that we genuinely don’t. We talk about stuff like what we are getting for tea. Becky tries to make me eat more veg. She literally does. I call her Mum.”

When the rump of the Parliamentary Labour Party (PLP) meets next week, contenders will be jostling for position in the knowledge that they will need 20 fellow MPs to have a chance of even being nominated. In a smaller party on the Commons benches, that may prove difficult for some.

Boris Johnson boasted on Friday morning that he had fulfilled his pledge to go ‘Corbyn neutral’ by Christmas. The Labour leader will probably still be in office over the festive break, until the ruling National Executive Committee (NEC) meets in January to set an election timetable.

One veteran party insider said that the next few days would see all contenders paying tribute to Corbyn while being careful to stress a radical break was needed from his leadership. “The fact is that in this election, we didn’t just lose votes to the Tories, we lost them to Lib Dems, the SNP. We lost Leavers and Remainers. It was about the party direction. It’s not about the so-called project, it’s who can win.”