In America they call it The Perp Walk. It’s the moment when the police triumphantly parade a suspect in front of the waiting media to signal to the world: ‘We’ve got our man.’

Yesterday morning, as Wes Streeting strode confidently along Downing Street following his ‘cup of coffee’ with Keir Starmer, it was clear he had finally made up his mind to go and get his man as well. The Prime Minister of the United Kingdom.

One minister who was watching on television at the time told me: ‘Wes is the smartest communicator in Government. He understands optics better than anyone. He wouldn’t have done the Downing Street perp walk if he wasn’t running.

‘And he also knows his Labour history: He’s not going to end up looking like David Miliband, standing there like an idiot with a banana.’

This was a reference to the former Foreign Secretary’s abortive 2008 Labour conference leadership coup, where his attempt to plunge a dagger into the back of Gordon Brown ended with his supporters vanishing at the 11th hour and David (elder brother of Ed) being photographed wielding nothing more deadly than a piece of fruit.

Today, Streeting’s hand will not be stayed. ‘It’s happening,’ a senior Government source told me. ‘Wes is going for it.’

According to his supporters, the Health Secretary was genuinely reluctant to directly challenge his leader. As late as last week, Streeting’s allies were telling me had no intention of triggering a contest ‘unless everything falls apart’.

But then three things happened. The first was that, on Monday, things did indeed fall apart. Keir Starmer’s latest ‘reset’ speech – planned by No 10 for more than five months – fell flat on arrival. The Parliamentary Labour Party could take no more. Almost 100 MPs, ministers and junior ministers took to the airwaves and social media to call for the PM’s resignation.

In the eyes of one Starmer loyalist, ‘that was all organised by Wes himself. He’s been planning it for months.’

Which may be partially true. But what’s also true is the anger that came pouring forth from Labour MPs in a well-choreographed wave across the party – especially from those members aligned with each of the main leadership campaigns.

The second issue that compelled Streeting to act was Starmer’s bizarre conduct at yesterday’s surreal Cabinet meeting. Faced with open revolt by his MPs and calls from his own most senior ministers to set out a timetable for his departure, he point-blank refused to discuss the issue, and instead told his stony-faced ministers they could discuss the issue in person with him at the end of the meeting.

According to a senior Government source, three ministers – including Streeting – attempted to take him up on his offer. At which point the Prime Minister turned tail and physically walked away from them. ‘That was just ridiculous,’ a Streeting supporter said. ‘The Prime Minister was refusing to even speak to his own Health Secretary. How can you run a government like that?’

On Tuesday evening Starmer finally relented and agreed to a meeting with Streeting yesterday morning. It lasted precisely 16 minutes and, while the details currently remain a closely guarded secret between the two men, one MP close to the Health Secretary told me: ‘Wes was blunt. He didn’t specifically tell Keir he had to go. But he set out the political reality and told him the current situation simply wasn’t sustainable.’ They added tartly: ‘The Prime Minister had a different perspective.’

Even this rebuff, however, wasn’t what pushed Streeting over the edge. Throughout the morning a series of increasingly aggressive briefings emerged from Downing Street, taunting Streeting for ‘bottling it’. As one Cabinet colleague observed: ‘No 10 had the chance to hug him close and bind him in. Instead they’ve spent 24 hours pouring vitriol on him and taunting him. It’s obvious the streetfighter in him will want to hit back.’

Today, he will. Yesterday saw a temporary ceasefire in Labour’s increasingly vicious civil war as the warring factions stepped back to allow the King to address parliament.

One Westminster observer likened it to the World War I Christmas truce, when German troops unveiled a conciliatory banner saying ‘Gott Mit Uns [God Is With Us]’ and British troops responded with their own: ‘We’ve Got Mittens Too.’ But hostilities are about to recommence in earnest.

While all eyes will be on Streeting today, ears will be turned in the direction of Manchester, where the drum beat from the Andy Burnham camp is getting louder. According to allies he will today announce he is mounting his own bid for the Labour leadership. ‘He’s moving when Wes does,’ a supportive minister said. ‘He’s going to declare he’s found a seat and he’s seeking to return to Parliament.’

Throughout yesterday Burnham was subjected to his own aggressive briefing thanks to the Downing Street spin operation, which insisted: ‘Andy hasn’t got a way back. He’s failed to get a seat lined up.’

Team Burnham intend to prove them wrong – although it’s not yet clear whether he will specifically identify the constituency or the MP prepared to step down for him.

Given No 10’s taunts, some allies believe he needs to furnish that detail. ‘He’ll have to actually name the seat,’ one told me. ‘There’s lots of scepticism.’

Even if Burnham does identify a seat, there are still doubts about whether he will be allowed to run for it, given Starmer’s once vice-like grip on the Labour party’s ruling National Executive Committee. But that grip may be starting to loosen.

Yesterday – in an unprecedented move – the 11 affiliated Labour Trade Unions issued a statement calling on Starmer to open a process to ensure his managed departure from Downing Street – which in turn indicates the influential union executives on the NEC may no longer be willing to do the PM’s bidding and block his heir apparent in the way they did in advance of the Gorton and Denton by-election.

As one minister with close links to the unions told me: ‘Keep an eye on the NEC. Things are happening there. Moves are afoot.’

Yesterday Keir Starmer’s team were confidently briefing they had seen off the threat to his leadership. But this morning that confidence looks set to morph into hubris.

Their goading of both Streeting and Burnham looks set to rebound on them. ‘Put up or shut up’ has been the taunt from No 10. And it looks like both men now have no choice but to take up the Prime Minister’s challenge.

Last night it was far from clear whether Wes Streeting will secure the necessary support to take his campaign to unseat Starmer to the Labour membership. Or if Andy Burnham will have locked down the seat that will enable him to amount a triumphant march to power.

As one Keir Starmer ally told me: ‘Wes doesn’t have the numbers and Andy doesn’t have the numbers. And when people see that, it’s over.’

For the Prime Minister’s sake, they’d better be right. Because if they’re wrong, Labour’s civil war is about to reach the doors of Downing Street.