The PM need work no more on his patient, calm, Government of Service persona. It has achieved the perfection of the pulpit; gleaming with episcopal polish.

He rose to the despatch box and laid before the House with simplicity, humility, and (were we imagining it?) a hint of submission to the eternal, the murdered David Amess, a dead general, a Holocaust survivor, and Alex Salmond. Ah, yes, what a hole he left behind him.

Sir Keir’s famous idea is that he and his Cabinet constitute the grown-up Restoration. But his clerical calm is (with thanks to Julie Burchill’s formula), a child’s idea of what a grown-up is. As most of us discerned from the age of nine – grown-ups are not just boring and evasive but essentially fraudulent.

So, the pleasure it gives is very considerable when the Prime Minister is rattled out of his piety, to reveal a familiar and slightly rat-like political character within.

It was this that, with considerable House of Commons skill, Rishi Sunak manouevred him into showing us all.

Rishi noted China’s militaristic exercises in the Taiwan Straits, and got a slightly unsteady answer. He brought up David Lammy’s forthcoming visit to Beijing and got a neatly packaged response. He brought up the Foreign Influence Registration Scheme that would detect and deter China’s attempts to intimidate and coerce our citizens and said that the Government was declining to implement it. Then he asked one of those lethal, one-word questions: “Why?”

Yes, good question actually. Why?

The PM stood. He paused. He summoned an answer. Nothing arrived. The political Deliveroo had gone to the wrong address. Keir mustered any eloquence he could and said, “That isn’t … correct.”

And to cat calls, hooting, cries of astonishment, he sat down. It was a loss of face that even Gordon Brown did not suffer.

He might have got away with it by invoking the sacred bond of secrecy between a prime minister and his security service, but he isn’t quick like that. He is calm. He is stable. He is patient and serious. He is not agile.

Rishi had more. He deposited, en passant, a poisonous little barb under the prime minister’s skin: “If he is going to give the security forces the tools they need, I would urge him to get up to speed on this.”

The courteous manner was particularly cruel and gave additional pleasure to aficionados of parliamentary brutality.

But then the finale. The Freedom of Speech Bill of the previous government would have protected universities from the (actually shocking) degree of political and intellectual suppression China has bought for itself in Russell Group universities. This is well known and has a dimension of national security to it.

The PM now actually stuttered. He said he didn’t think this was a suitable area for party political points. That is what he said. Protecting the speech rights of indigenous students against the imperial reach of a foreign power was a party political point. And for once, the backbench howling and front bench cringing (indeed, very talented, almost experimental howling and cringing) destabilised him. He limped off in entirely the wrong direction:

“Throughout the last Parliament we stood with Government on all matters of security.” He tried to gain some purchase on the argument. “I worked with the security and intelligence service for five years, prosecuting cases. I know first hand the work they do, as a lawyer. And as prime minister. And he knows that.”

The, “And he knows that,” as he sat down produced actual, non-performative cringing. It was within the three most embarrassing moments of a generation. We must be grateful to the PM for allowing us into the inner sanctum of his psyche (and for allowing us out again).

The mortification – which should have been good for the episcopal soul – pushed him into a childish conclusion. “He talks about the last government…” he began and then we were off China, national security and WWIII and back to utter failure, fewer choices, foundation-fixing and giving the country its future back.

Not calm, not patient, not serviceable.

NB: Alex Smith (L) set back her career in the party by a full parliament as she urged the abolition of the hereditary principle. Has she no idea how the Labour party works?