Theresa May flung Marx at Jeremy Corbyn: “Those are my principles, and if you don’t like them… well, I have others.”

That comes, she reminded the House, not from Karl but from Groucho, and applies all too well to this malleable Leader of the Opposition, now reduced to following his Remainer colleagues.

Corbyn cannot speak with authority, and usually evades, as too difficult, whatever the issue of the hour may be. Today he took refuge in a worthy sequence of questions about legal aid.

Once we get a new Prime Minister, there will surely have to be a new Leader of the Opposition, capable of holding the Government to account, and plausible as an alternative PM.

The age of May and Corbyn will become, perhaps, a shadowy period, over which historians will pass in a sentence or two.

The sense of things coming to an end was intensified by the Prime Minister’s expression of “great regret” at the resignation of Sir Kim Darroch from the post of Ambassador in Washington.

David Lidington, sitting on one side of May, nodded with unbounded and repeated emphasis as she said this.

Philip Hammond, sitting on the other side of her, nodded ever so slightly. The Chancellor of the Exchequer is not a demonstrative man, and can seldom be found lamenting others’ misfortunes.

May accused Corbyn of doing “his best to ignore the anti-semitism in his party”, and pointed out that Lord Triesman and two other Labour peers have just resigned from the party because of this.

She remarked that Labour’s cry used to be “education, education, education”, but now “it’s just tax, tax, tax, injustice, injustice”.

Corbyn had already said he is “totally committed to eliminating racism in any form”. But if this is so, why have the three peers gone?

PMQs went on for too long. The Speaker has got into the habit of allowing as much time as backbenchers need to get a fair crack of the whip.

The same effect could be achieved if everyone asked shorter questions. The House has become self-indulgent. MPs no longer concentrate on expressing themselves with the greatest possible concision and force.

They ask long-winded questions, which give the Prime Minister longer to think, and more chance to evade the heart of the matter by rambling on about inessentials.