It’s not a case of whether Boris Johnson will go, but when and how

For some senior Tories, the only questions now are "how" and "when" Boris Johnson is forced out after the most damaging revelations to date about Downing Street parties.

So who would wield the knife? There’s already talk in Westminster that Tory backbench leaders – the executive of the 1922 committee – will send a delegation to Johnson to tell him his time is up.

But there is another scenario, involving the cabinet. Significantly, silence was golden yesterday, when no cabinet member came out to defend the prime minister. No minister, not even an ambitious junior ready to suck it up on the short straw, is on the airwaves this morning. Message to PM: “Sort out your own mess. For goodness sake, say sorry. For once, look like you mean it, and don’t smirk.”

As the new year began, Johnson thought he had his cabinet where he wanted it. His tactic was to divide and rule, so his party would stick with him. As one Johnson ally whispered: “He’ll let Rishi Sunak take the blame for tax rises, while handing the Europe brief to Liz Truss makes it hard for her to keep the Brexiteers onside.”

Johnson would, meanwhile, use Covid to rebuild bridges with Tory backbenchers. On Monday, he was preparing to trumpet a more optimistic briefing to ministers about the Omicron wave by Chris Whitty, the chief medical officer. Then the leaked email with the May 2020 party invitation emerged, and Johnson’s fightback was blown out of the water.

When Johnson’s authority waned before Christmas, the cabinet assumed real power for the first time under his administration. It, and not Johnson, is now calling the shots on Covid. That is why England avoided the further restrictions seen in the rest of the UK. “We have ended rule by Sage,” one minister told me.

Although Michael Gove said Johnson’s “judgment has been vindicated” on the need for no more curbs, insiders say it was the cabinet’s judgment rather than the PM’s, when he conceded a three-hour cabinet discussion in a break with Number 10’s usual practice of bouncing ministers into rubber-stamping decisions already taken. Pressure from ministers is now driving moves for the isolation period to be cut from seven to five days and for most restrictions in England to end on 26 January rather than be renewed. It is not just about Covid. “The cabinet is now in charge of policy,” said one Whitehall insider.

Johnson’s conversion to traditional cabinet government is probably skin deep, born out of necessity rather than conviction. But his crisis is deepening and he won’t be able to turn the clock back. Suddenly, he needs his cabinet more than it needs him. He knows it could save him but that it could also break him.  He was shaken by the resignation of his ally David Frost as Europe minister and knows he cannot afford another one in the current febrile climate.

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It was the cabinet which forced Margaret Thatcher’s resignation in 1990, even if her ministers were reflecting the view of Tory backbenchers who (just like today’s increasingly nervous crop) thought she would cost them their seats after turning from electoral asset to liability.

For now, cabinet ministers are not saying Johnson must go. Resigning might backfire if others didn’t follow and Johnson survived; it might be safer to let backbenchers do the dirty deed. It is harder to prise a PM out of Number 10 than it looks. But ominously, Johnson’s would-be successors are making preparations for a leadership contest in case he does go. Such moves do not always end in a downfall but they are part of the process when it happens.

The cabinet could yet save Johnson from his own mistakes and incompetence, which ministers couldn’t do when decisions were imposed by Downing Street. I suspect cabinet debate would do much more to improve his dysfunctional operation than the much-predicted shake-up of Number 10 advisers. If all the big decisions are taken in the Downing Street bunker, then there is no one to take a fresh look, spot the pitfalls and challenge the groupthink. Crucially, cabinet ministers can stand up to Johnson – and are now doing so – in a way his current aides plainly cannot.

When might Johnson go? It could happen very quickly if Tory support continues to drain away at its current rate. But some old heads are urging colleagues to wait, and not saddle a new leader with blame for the cost-of-living crisis. There’s also a feeling that Sunak and Truss are not ready yet and need time to prove themselves. There’s always a chance a wild card will come up. Watch Nadhim Zahawi.

So Johnson might limp on until the May local elections, when his enemies within would hope that poor results deliver the final blow.