No phrase in British politics is more calculated to harm than that uttered by Leo Amery to Neville Chamberlain in the Norway debate of 1940: “You have sat too long here for any good you have been doing. Depart, I say, and let us have done with you. In the name of God, go!” Amery was quoting Cromwell’s injunction to the Rump parliament in 1643. Yesterday it was redeployed against Boris Johnson in the Commons by veteran backbencher and fellow Brexiteer David Davis.

The effect was electric, not least as it came just minutes after Christian Wakeford, the Tory MP for Bury South, had defected to the Labour Party, the first to do so since 2007. Mr Wakeford then sat directly behind Sir Keir Starmer, the Labour leader, in a piece of stage-managed political theatre that for a moment united Tories in their denunciation of the turncoat.

But Mr Davis’s intervention was far more damaging to the Prime Minister given the MP’s standing among the Brexit wing of the party and as a former leadership candidate and minister. It was Mr Davis who was the first to resign from Theresa May’s Cabinet, precipitating the events that led to her downfall. His brutal assessment of the Prime Minister’s integrity drew parallels with Sir Geoffrey Howe’s devastating attack on Mrs Thatcher in 1990 that led to a leadership challenge and her resignation just weeks later.

Mr Johnson’s fate now depends on the party’s reaction to the findings of a report by Sue Gray, a senior civil servant, into the alleged rule-breaking at Downing Street during the lockdown. Even a hint of criticism will be hard for him to withstand. A motion of no confidence requires the support of 54 MPs, but if this is now being orchestrated by the likes of Mr Davis that no longer looks too high a hurdle to overcome. Nor can it be dismissed as a “Remainer plot” to unseat Mr Johnson as it cuts across the party, from Right to Left, North to South, new MPs to old stagers.

It is a shame that this melodrama distracted from what was otherwise a red-letter day, with England becoming the first major country in Europe to remove most Covid restrictions. Mr Johnson announced that the Plan B controls introduced before Christmas in the teeth of opposition from 100 of his own MPs, were being scrapped.

Mask wearing by secondary school children in the classroom will end forthwith and should never have been countenanced. Face coverings will no longer be needed in shops and public transport, and work-from-home guidance is withdrawn, along with Covid passports for nightclubs and large events.

The legal requirement to self-isolate after a positive Covid test does not expire until March 24 and a parliamentary vote is needed to bring that date forward. That should be done immediately if the Government is serious about trusting people to live with Covid as they do with flu.

Essentially, the pandemic is over, even if its end has not formally been declared and there are currently more cases than at its height. There are 750 people in intensive care and overall deaths are below the average expected at this time of the year. Even so, other parts of the UK, which introduced tougher restrictions, are being scandalously slow to unwind them, despite the negative impact on their economies.

The milder omicron variant has not translated into the rise in hospitalisations and fatalities feared by scientists, whose doom-mongering has again been confounded. The big remaining problem is not that the NHS will be overwhelmed by ill patients but that it does not have enough staff because so many are isolating. This is going to get worse when the NHS starts dismissing 80,000 doctors, nurses and ancillary employees who refuse to have the vaccine. Mr Johnson was unapologetic, given that they will be treating older and vulnerable people for whom Covid remains a threat. They must get the jab, he told MPs. But what if they don’t?

Tory MPs gunning for Mr Johnson should consider that the UK is one of the world’s best protected nations because of the vaccination programme for which he can claim much credit. His instincts have been with those who want fewer, not more restrictions, even if he has felt obliged to fall in with scientific advice that has subsequently proved to be too pessimistic.

No prime minister since the war has been dealt such a difficult hand, and who is to say they would have played it any better? Nonetheless, as Churchill discovered, there is little sentimentality in politics and Mr Johnson still faces the prospect of a vote of no confidence.

He might forestall this by setting out a compelling set of arguments for leading the Tories into the next general election. With the pandemic dwindling, the economy will take centre stage. Rising inflation, tax increases and high household energy costs will put a brake on the economic growth without which not much else is possible. The party needs a competent free-market, low-taxing, small-state, outward-looking, freedom-loving Conservative at the helm. Mr Johnson has to demonstrate he still merits that job description.