Neville Chamberlain had to go. That at least was clear. The Norway Debate in 1940, to which reference was made by Jacob Rees-Mogg and others, was in theory about whether or not the House should adjourn for a few days at Whitsun, but in practice about whether the Prime Minister had the support needed to survive.

No wonder Theresa May looked so white, tense and hunched as she sat on the Treasury Bench for the last half hour of today’s debate. Her hands were folded in her lap so the tips of her fingers touched each other, and scraped crab-like against each other.

The Chief Whip, Julian Smith, sat down next to her, and spoke very quietly in her ear. A few minutes earlier he had been at the other end of the Chamber, talking to Rees-Mogg.

And a few minutes earlier, Dominic Grieve, the drafter of the rebel Tory amendment, had declined to jump off the cliff, or to throw the Government off the cliff.

He had instead backed down. That meant the Government was almost certainly going to be all right. But in May 1940, Chamberlain won the vote. His majority was, however, so reduced that he himself was not all right.

Perhaps that was why the Prime Minister and the Chief Whip looked so grave as he spoke to her. There is such a thing as a Pyrrhic victory.

Labour was miffed that Grieve had backed down. Hilary Benn, one of those natural frontbenchers who is for some reason on Labour’s backbenches, advised him to be “very, very cautious” about accepting the Government’s assurances.

Sir Keir Starmer, from the Labour front bench, had earlier tried to launch a new catch phrase: “And the sky did not fall in.”

He said this was what happened, or did not happen, when the Government had made previous concessions on the Withdrawal Bill.

So it would be fine to force the Government to make further concessions now. Grieve could defeat May and the sky would not fall in.

Grieve, rather prudently, did not buy this. He may well have thought the sky would fall in on him, which would do no one any good.

He warned, darkly, that the sky could still fall in: “Those whom the gods want to destroy they first render mad. There’s enough madness around at the moment to make one start to question whether collective sanity in this country has disappeared.”

Moreover, Grieve said, The Daily Mail “is crawling over the garden of my house in France”.

Anna Soubry, who sounded huskier than usual, suggested, one felt only partly in jest, that the editor of The Daily Mail has “a small doll which looks like me and is sticking pins in my throat”.

George Howarth (Lab, Knowsley) was just comparing Grieve to the Grand Old Duke of York, who marched his men to the top of the hill once too often, when the vote was called, which the Government won by 319 votes to 303.

A win is a win, but how precarious the whole thing looks. Everyone wonders what will happen, and nobody knows. But for the time being, May’s show is still on the road, and the weaker she looks, the more inclined her own MPs could be to let her keep inching her way forward.