Jeremy Corbyn bore a more distressing resemblance than usual to Wilfred Bramble playing Steptoe. He failed to congratulate Gareth Snell, Labour victor in the Stoke by-election, who was in the House, and then found himself obliged, immediately after PMQs, to see Trudy Harrison, Conservative victor in Copeland, being sworn in, to loud Tory cheers and wavings of the order paper.

Corbyn accused the Prime Minister of having “sneaked out” changes in mental health benefits. He could not make the charge stick, in part because there was nothing sneaky about May, but mainly because he sucks the energy out of whatever subject he touches.

He is not just an anti-hero but an anti-leader: a man who appears to be retreating even when he advances. It is odd that he has not been shot in the back by his own troops: but then one recalls that they passed an overwhelming vote of No Confidence in him, and he refused to step down.

May treated the subject of mental health with proper respect. She also treated with respect those Labour backbenchers who asked serious questions on serious matters.

She even marked St David’s Day by saying a few words in Welsh. For all we know, it may not have been very good Welsh. But the sincerity of her effort somehow commanded respect.

So too with her jokes: about eight times out of ten, one feels she has not been very funny. But her conscientiousness still carries through.

And yet it is bad even for her to face such a feeble opponent. It is like playing tennis week after week against someone who cannot get the ball back over the net: you win an interminable series of easy victories, but your game is bound in time to lose its edge.