Absence does not always make the heart grow fond. Parliament’s five-week summer recess permitted the Starmers to recharge in a rented cottage whilst the prime minister’s croft and camping trip to Scotland – never intended to be long – was curtailed when the Mail on Sunday revealed where it was pitched. Even some who are not minded to cut Boris Johnson much slack felt that he might have been allowed a full week’s respite during which he could get to know his infant son after a first year at Downing Street that has had no lack of incident. But no such luck. Those whom the gods wish to destroy they first make prime minister.

PMQs returned today, and on this showing, Boris Johnson’s mistake was not spending the entire recess in a luxury spa resort in a very distant land where press censorship is ruthlessly enforced but the mattresses and pillows are soporifically soft. Beyond u-turns, there has been little that is positive to show for the hours he instead spent at his desk during the recess and the impression he gave in the Commons today was of an aggressive bear with an especially sore head. Testy, shouting, evasively unwilling even to pretend to answer the question and – after he had passed on his best wishes for his birthday – gratuitously rude to the leader of the Opposition, this was comfortably Boris Johnson’s least uplifting PMQs performance.

It was a racing certainty that Starmer would ask about the school “exams fiasco.” On Tuesday, Gavin Williamson, had stated that he had received advance indications of problems with Ofqual’s algorithm and the Labour leader wanted to know when the prime minister – who on the day the original results were issued described the system as “robust” – was informed that “there was a problem with the algorithm.”

There was no good answer to this. If Johnson admitted to being in the loop, then why had he not intervened earlier? But if he claimed ignorance then, well, that is not a good look either. So he opted to make no pretence at answering the question. Predictably, Starmer therefore asked it again.

Johnson again refused to answer, instead trying to pass the blame on to the Labour leader who “all summer long he has been going around undermining confidence, spreading doubts, particularly about the return to school in safe conditions.” The accompanying shouts and jeers from the Labour benches appeared to energise him to go further. “Today is a great day because the parents, pupils and teachers of this country are overwhelmingly proving him, proving the doubters wrong, because they are going back to school in record numbers.”

Those whom the gods wish to destroy they first make prime minister.

“The prime minister is tin-eared and just making it up as he goes along” the Labour leader responded in a tone of supreme weariness. “He’s just playing games and he’s fooling nobody” as the moaning from his own Tory backbenchers proved.

The mention of u-turns drove Johnson into a state of fury. Gladly abandoning the exchange on schools, he launched into a campaign-stump diatribe. “This is a leader of the Opposition who backed remaining in the EU and is now totally silent on the subject. Now he has performed a u-turn. Perhaps he still does [want to remain], Mr Speaker? This is a leader of the Opposition who supported an IRA-condoning politician who wanted to get out of Nato. This is a leader of the Opposition who …”

At this point The Speaker called the prime minister to order and reminded him to answer the question. Eventually Johnson got around to saying that Starmer was “Captain Hindsight, leaping on a bandwagon and opposing a policy he had supported two weeks ago.” Labour had opposed the teacher-accreditation system eventually used. Did they or did they not now support it? By now Labour MPs were in full shout. Ominously, Tory members sat in silence.

Johnson’s jibe about the Labour leader having stood by his IRA-sympathising predecessor worked in the sense that it deflected Starmer from probing further on the school exams shambles – to which the prime minister clearly had no answers. But it lost the prime minister the respect of the house. When Starmer asked him to “have the decency to withdraw that comment,” he merely dug deeper, suggesting that “the protestations of the right honourable gentlemen would have been more in order throughout the long years in which he supported the leader of the Labour party”.

By now the former Director of Public Prosecutions was doing a convincing impression of a very angry man, flashing back “when the prime minister has worked with the security and intelligence forces prosecuting criminals and terrorists he can lecture me. I asked him to do the decent thing, but doing the decent thing and this prime minister do not go together.” This has been “a wasted summer” Starmer began to perorate. Crisis had followed crisis and after twelve u-turns “the only conclusion is serial incompetence.”

If these exchanges started as honest knock-about they are in danger of escalating into knock-your-block-off. Johnson’s tactic is obvious. Starmer sees himself as a man of unbending integrity, a truth-seeker using his forensic legal skills to cut through the obfuscation of a prime minister who thrives on political sentiment rather than administrative detail. Johnson does not share Starmer’s self-estimation and enjoys suggesting that he is not as great as he cracks himself up to be. Johnson wants to radiate energy and positivity and in doing so paints Starmer as a man with few ideas but a small-minded, legalistic, readiness to find fault, any fault, in the endeavours of the can-dooers.

But PMQs are about prime ministerial answers. If Johnson offers none beyond mocking and sneering at the leader of the Opposition he forfeits the opportunity to present himself as a dynamic, positive and good-natured statesman. He instead looks like a bully who makes a noise to distract from his own inadequacy. Boris Johnson would do well to recapture some of his charm, bonhomie and positivity. Because without it, what is his shtick?