Stabbed in the back by David Davis! Until this moment, near the end of PMQs, Boris Johnson had just about kept his end up.

Davis told him: “You have sat there too long for all the good you have done. In the name of God, go.”

Johnson affected not to recognise the reference, but these were, as he well knows, the words used by Leo Amery in 1940 to tell Neville Chamberlain the time had come to get out of Downing Street.

Chamberlain, whose reputation never recovered! Chamberlain, who was forced to make way for Winston Churchill!

There is no Churchill waiting in the wings to take over from Johnson. But for a senior Conservative backbencher, and former Cabinet colleague, to denounce him at this moment of greatest danger was a grievous blow.

Chamberlain still won the vote in 1940, but with a majority so reduced he was no longer credible, and was obliged to recognise that having until recently dominated the Conservative Party, and commanded wide support from the public for his policy of appeasement, he could not now carry on.

Immediately after PMQs, Johnson delivered a statement in which he said the Government will no longer mandate the wearing of face masks. His policy, as he repeatedly pointed out, is succeeding.

And Sir Edward Leigh (Con, Gainsborough), a backbencher of long service, told him, “to paraphrase Leo Amery, for God’s sake, keep going”.

To which Johnson replied: “I haven’t sat here quite long enough, indeed nothing like long enough, in my view.”

That was more like the old Johnson. Perhaps he will start once more to play his natural game of ridiculing his opponents as a bunch of prigs.

The difficulty he found as he exchanged blows at PMQs with Sir Keir Starmer is that he, Johnson, had to adopt a sombre, contrite, somewhat priggish tone in order to show he feels the pain of those who obeyed the Covid rules while their loved ones died.

At the start of PMQs, Christian Wakeford, until a few minutes earlier Conservative MP for Bury South, took his place on the Labour benches.

Sir Keir started by “warmly welcoming” his new recruit, and then joined in the ancient British blood sport, engaged in with particular enthusiasm by the feral beasts of the media, of hunting down the Prime Minister.

As one of North London’s most distinguished human rights lawyers, the  Leader of the Opposition is not really a blood sports man. He is willing, however, to make an exception in the case of Johnson, and began by making a joke about the Conservatives who were heckling him: “I’m sure the Chief Whip has told them to bring their own booze.”

Drink is indeed a feature of the hunting field. Sir Keir laughed at his own joke, cantered off in as natural a manner as he could manage in pursuit of Johnson, and directed several cutting if rather legalistic jabs at him.

Johnson showed flashes of the fighting spirit which a hard-pressed Prime Minister simply must show on an occasion like this, declaring in a trenchant tone that “we will win again in Bury South at the next election under this Prime Minister.”

Then came Davis. Not good for the PM. On the other hand, although Johnson announced a medal for the evacuation of Kabul, at least we are not about to evacuate Dunkirk.