“He is, like me, a living testament to the benefits of moderation in all things.” What a tricky opponent Boris Johnson is. He set out to show the world that he and Ian Blackford, to whom this remark was addressed, are on such cordial terms that light-hearted references to their struggles with their weight are in order.

Nothing could be more damaging to Blackford, leader of the SNP at Westminster, than to be exposed as a friend of the Prime Minister.

Johnson is not popular in Scotland. SNP activists live in hope that the Prime Minister may arouse such antipathy north of the border that their cause triumphs.

But what if affable, comfortable, companionable Scots such as Blackford instead indicate, by their demeanour, that when they come down to London they rather enjoy the Prime Minister’s company, and even find it preferable, as well one might, to that of the most embittered and distrustful cybernats?

Blackford did his best. He accused Johnson of last night throwing a “champagne bash” for Tory MPs just as millions of families were worrying how they will manage to pay “the £700 energy price hike”.

Johnson refused to be riled. His manner indicated that he regards Blackford with fond amusement.

What now is Blackford to do? For the angrier he sounds, the more amused Johnson will be, and the more inclined to show he knows Blackford is only pretending.

Sir Keir Starmer, for Labour, began well, with a short and pointed question: “Does the Prime Minister still think he and the Chancellor are tax-cutting Conservatives?”

Rishi Sunak, who was sitting beside Johnson, smiled, but it was the smile of a bruised man, pained by the denunciations in the last week of him and his Spring Statement.

Quite soon, Johnson was being genial at Sir Keir’s expense: “I don’t know where he’s been for the last two years.” How extraordinary that Sir Keir could have managed “to obliterate the biggest pandemic for the last century from his memory”.

A derisive remark, yet not delivered in a mean-spirited tone. Johnson was robust, genial, almost amused by “this human weathervane” who one week thought the Prime Minister should stay in office but the next week wanted him to go.

What a cunning adversary Johnson is. For if one turns up the volume of one’s attack, one may start to sound rather vicious and lacking in sense of proportion, while there he is, magnanimous and moderate, refusing to take it personally, altogether, perhaps, a more enjoyable person with whom to have a drink or two afterwards in the pub.

Matt Western (Lab, Warwick and Leamington) had a convoluted crack at the Chancellor, “so out of touch he’s contactless”.

Johnson replied in a friendly tone that “much as I admire his style”, the question would work better “as a light essay in The Guardian“.

What lack of rancour! Even references to the Downing Street parties did not spoil his mood. One might as well try to get Bertie Wooster to take a dim view of that beano last night at the Drones Club.