FINALLY, the Downing Street One realised that barricading himself inside the Cabinet Room and shouting to colleagues through the keyhole: “B*gger off. I’m not coming out!” was not sustainable.

Boris Johnson’s limpet-like defiance ended when some of his most loyal ministers were able to break down the door and prise his fingers from the Number 10 furniture. The blonde Houdini had to accept, for once, there was no escape from reality.

With the flow of resignations continuing yesterday morning, hitting over 50 in just 48 hours, it was becoming clear that there was no functioning UK Government. The Education Department, for example, had no ministers. Michael Gove, the Levelling-Up Secretary, was sacked after telling the PM his time was up, which earned him Downing Street’s disdain; it branded the Scot a “snake”.

More Cabinet members resigned; Simon Hart, Brandon Lewis and Michelle Donelan, the respective Secretaries of State for Wales, Northern Ireland and Education; the latter for just 35 hours.

The powerful sound of a long silence from Downing Street yesterday morning suggested, rightly, something was afoot.

Nadhim Zahawi, only appointed Chancellor 48 hours earlier, demanded Johnson, whom he had steadfastly supported for so long, “go now”.

The PM’s downfall has been a slow-motion car crash since he entered Number 10; through the scandal of Partygate, the loss of not one but two ethics advisers and the Paterson paid-advocacy row.

But the endgame was unexpectedly triggered early Tuesday when Lord McDonald, the Foreign Office’s ex-top official, revealed how, in 2019, Johnson had been told “in person” about a specific allegation of misconduct against one of the department’s ministers, Chris Pincher.

This completely contradicted Downing Street’s line, which, initially, was the PM knew nothing about any previous allegation, then that he had heard about a general one but it had been “resolved”; a euphemism. In fact, the allegation against Pincher was upheld. Despite this, the Johnson ultra-loyalist continued in his ministerial role and was later promoted to Deputy Chief Whip.

Having been seemingly caught red-handed in lying to colleagues, who were sent onto the airwaves to protect the PM, what did Johnson do? He said that 2019 was a busy time and he had forgotten about Pincher’s upheld complaint. Then, attempting to redeem himself, the PM apologised and admitted he had made a mistake in not quickly ditching his colleague. For many who had put up for too long with their leader’s dysfunction and duplicity, enough was enough. Once Sajid Javid and then Rishi Sunak had resigned in an apparently carefully co-ordinated strike, the cascade of resignations began.

Nicola Sturgeon said there would be a “widespread sense of relief” at the PM’s decision to resign as Tory leader. Nowhere more so than among Scottish Conservative MPs, facing decimation at the 2024 General Election under Johnson’s leadership.

Even in announcing his forced departure, the PM, who by his own actions had squandered the 80-seat Commons majority he won in 2019, proved how divisive a character he is.

Not a hint of humility in his Downing Street speech yesterday for his dishonest approach to government but, instead, defiance, blaming the “herd instinct” of colleagues and their “eccentric” decision to oust him from office. The insults will do nothing to rally them around his desire to stay on as PM until the autumn when a successor will be chosen. Despite Johnson appointing new members to fill the Cabinet holes, a swell of Tory opinion is growing for his tainted premiership to end within days and a caretaker premier appointed.

Ex-PM Sir John Major said it would be “unwise” for Johnson to hang around for several more months. What could possibly go wrong?

Keir Starmer – who yesterday looked relaxed in the royal box at Wimbledon – announced that if the PM didn’t go swiftly, Labour would seek a confidence vote in the Government. If it won, it would spark a general election. However, it was just political theatre; the move won’t succeed. The last thing Tory MPs want – in light of Johnson’s forced departure and the recent humiliating by-election defeats – is a snap poll, which the Conservatives could lose. So, they will use their 73-strong Commons working majority to defeat the Labour gesture.

Johnson’s departure fires the starting-gun on a Conservative cavalry charge. Some candidates will be more credible than others. Several will throw their hats in the ring, hoping to get a job in the new administration.

Zahawi, the newly-minted Chancellor, will be a serious contender but some might feel he had a despicable plan to secure a quick promotion just to position himself for the top job.

The seemingly co-ordinated strike of ex-Chancellors Javid and Sunak might signal they have agreed a Blair/Brown-style private deal and will effectively run on a joint ticket to maximise support across the Tory Party membership, which will ultimately decide on who succeeds Johnson.

Another contender, Liz Truss, cut short her trip to Indonesia to return home. The Foreign Secretary, who currently has majority support among the party grassroots, called for “unity and calmness”.

The winner in the Conservative succession race will be the person, who can convince colleagues and the wider party that, following the battered premiership of Johnson, they are the best person to unite the party, restore integrity to Government and implement a forward-looking and successful way through the cost-of-living crisis, the continuing Covid pandemic and the war in Ukraine.

At present, this might seem like Mission Impossible. Yet with two years to go to the next General Election, it may just be – given the Conservatives’ innate ability to unite in order to win UK polls – Johnson’s forced exit could be the first step in the Tory Party’s recovery and might give it a fighting chance of pulling itself out of the very deep hole it’s in by 2024.

In the end, Johnson paid a high price for putting ego above party and country and as he rightly noted in his farewell address from the steps of Downing Street: “In politics, no-one is remotely indispensable.”