What ebullience! What effrontery! What love of diversions and jokes! The Prime Minister looked and sounded like a man without a care in the world.

Nobody would have supposed, from his demeanour, that he was about to fly to Brussels for a crucial dinner with Ursula von der Leyen, President of the European Commission, on which could turn the whole question of whether or not Britain gets a trade deal with the EU by the end of the year.

Boris Johnson suggested we shall “prosper mightily” whether or not we get a deal. Lighten up, folks, it doesn’t really matter either way.

“A good deal is still there to be done,” he assured Sir Edward Leigh (Con, Gainsborough), but we shall not concede to “our friends” in the EU “the automatic right to punish us” if they pass some new law with which we refuse to comply.

That was about as serious as Johnson became. He needs to carry his own backbenchers with him. They, after all, have the power to get rid of him when they decide he has become a liability.

Sir Keir Starmer already considers Johnson a liability, but does not at the moment have the power to get rid of him.

Johnson wished Sir Keir “all the best in self-isolation in Islington, his spiritual home”, for the Leader of the Opposition was obliged, having been in contact with someone who has Covid-19, to appear by video link.

Sir Keir remarked that he lives in Camden, not Islington. The Prime Minister accepted this, indeed one can be pretty sure he already knew it, for he too has lived in North London man and boy.

The point was that he was going to pin on Sir Keir the damaging charge of being an out-of-touch member of the metropolitan elite, while the PM is on the side of ordinary people who like to have a good laugh at ridiculous North Londoners.

Sir Keir remarked that a year ago Johnson had promised us a permanent break from talking about Brexit: “Can the Prime Minister tell us how that’s going?”

Johnson counter-attacked by accusing Sir Keir of maintaining a “sphinx-like silence” on the question of Brexit. Sir Keir recalled that Johnson had said failure to get a trade deal with the EU would be “a failure of statecraft”.

The Prime Minister declared that Sir Keir was “totally delphic” on the question of Brexit. The same might be said of the PM himself: like the Oracle at Delphi, it was impossible to work out what he meant.

Here is a negotiator who does not believe in showing the world his cards. Only with the benefit of hindsight will it be possible to see what game he is playing.