Philip Davies (Con, Shipley) raised a question which troubles many Tory backbenchers:

“To paraphrase the late, great, much-missed Eric Forth, Mr Speaker, I believe in individual freedoms and individual responsibility, I believe that individuals make better decisions for themselves, their families and their communities than the state makes for them, I loathe the nanny state, and I believe in cutting taxes. Prime Minister, am I still a Conservative?”

In other words, Prime Minister, are you still a Conservative?

This is dangerous territory for Johnson. One day, when he is down on his luck, those Tory backbenchers will hold his fate in their hands, and not a few of them will say it all went wrong because he abandoned the true Tory faith as proclaimed by Forth and Davies.

Johnson took refuge in brevity: “Yes, Mr Speaker,” he declared with emphasis, provoking an appreciative laugh from the House, and left it at that.

Sir Keir Starmer had earlier attempted, like Davies, to indicate that the Prime Minister is not a true Conservative.

He reminded us that Johnson had promised not to cut the size of the armed forces, yet was now doing exactly that.

The Prime Minister retorted that the Army would still be 100,000 strong “if you include the reserves”, and made a crack at Jeremy Corbyn.

“Mr Speaker, he’s fighting the last war,” Sir Keir retorted, and pointed out that the regular army is to be cut from 82,000 to 72,500 by 2025, with cuts in planes, tanks and ships too.

Might Sir Keir be fighting the last war? None of us will know for certain until the next war comes and we discover whether we have the means to fight it.

The Prime Minister said it was “frankly satirical” to be lectured by Labour about the size of the Army, and mocked his opponent’s “new spirit of jingo”.

Sir Keir retorted that the Prime Minister lacked the “courage” to admit what was happening, or to put the cuts to a vote in the House.

So is the main charge against the PM that he is untrustworthy, that he is cowardly, or simply that he is not a Conservative?

The Leader of the Opposition has not yet decided where to place the Schwerpunkt, as Clausewitz would have termed it, of his attack on Johnson.

After all, the trouble with pointing out that the Prime Minister is not a Conservative is that this might increase his already quite noticeable popularity with Labour voters.