Boris Johnson had a bad first day back. While Sir Keir Starmer conveyed genuine moral indignation, the Prime Minister sounded like a schoolboy who has not merely failed to do his homework, but has not taken the trouble to think up any plausible excuses for failing to do it.

Starmer, in the manner of a teacher demanding proper answers from a disgracefully feckless pupil, began with “the exams fiasco”: “When did the Prime Minister first know there was a problem with the algorithm?”

There was no good answer, because as Starmer remarked, either the PM knew and did nothing, or did not know but should have known.

Johnson accused Starmer of “going round undermining confidence…spreading doubts…gloom and dubitation”. But this counter- attack was mounted in a lacklustre way.

Starmer proceeded to accuse Johnson of “making it up as he goes along” and “just playing games”, but there was in fact something oddly unplayful in the PM’s demeanour. He was not enjoying himself, and in the socially distanced Chamber, less than a tenth as full as it would be in normal times for PMQs, lacked the audience which might have spurred him into performing with brio.

The Speaker, Sir Lindsay Hoyle, was not amused: “We do need to have the answers.”

Johnson didn’t have them. He tried to dub Starmer “Captain Hindsight”, and accused him of having for years supported an IRA sympathiser, i.e. Jeremy Corbyn. Starmer retorted that “the problem is the PM is governing in hindsight”, and waxed wrathful at the slur that he had somehow supported the IRA, when actually he had spent years prosecuting it.

He demanded that Johnson have the “decency” to withdraw the IRA comment, but added that “doing the decent thing and the Prime Minister don’t go together”.

The PM was unrepentant. His hooliganism is reminiscent of Lord Randolph Churchill, father of Winston, who in the 1880s was almost unbelievably rude about Gladstone, but in a wittier way than Johnson today achieved.

So this was not a glorious half-hour. It showed instead the profound incompatibility between the PM and the Leader of the Opposition.

Starmer is bound to find Johnson disreputable, and was today successful in showing him up. Johnson is bound to find Starmer prosy and negative, and was today unable to make those charges stick.

Ian Blackford, for the Scots Nats, said on a point of order that Downing Street had accused the SNP of revealing the whereabouts of Johnson’s holiday cottage in Scotland: “this allegation and briefing was entirely and deliberately false”, “the worst kind of political smear”, should not have been engaged in by “the apparatus of the British Government”, and had led to threats against Blackford as the local MP.

Johnson replied in a light-hearted manner, whereupon the Speaker reminded the House in a grave tone of the “security implications”. So we see Johnson, by his impenitence, infuriating those who think life is real and life is earnest.