Week by week, Jeremy Corbyn develops a closer resemblance to his fellow north London resident, Mr Pooter. The Labour leader stands on his dignity. He waits for silence, when it would plainly be better to ignore the Tory hooligans and press on.

He hovers, perilously, on the edge of the ridiculous. Today Mr Corbyn told the House: “Mr Speaker, this isn’t about entertainment. This is not funny for people who are desperately worried.”

He was asking about tax credits, and was getting nowhere. Among the people who looked desperately worried were his own backbenchers. Week after week they watch their newly elected leader, and see no sign that he is going to score off David Cameron.

For there is about Mr Corbyn a kind of effortless inferiority. One feels he might go home and write with serene complacency in his version of Diary of a Nobody that although not everyone realised it, and certainly not those ill-mannered Tories, this week he really put Mr Cameron on the spot, by showing that the Prime Minister cannot guarantee that no one will be worse off as a result of the cuts in tax credits.

When Mr Corbyn was a dissident left-wing backbencher, it was quite enough that he stuck to his guns and said what he thought. He did not expect actually to change Government policy. He felt good about himself because he spoke out.

This seems to remain his attitude. One catches no desire to embarrass Mr Cameron in front of Tory backbenchers, or in front of those who glimpse some fragment of these exchanges on television. By renouncing “entertainment”, Mr Corbyn has renounced wit. To the great cause of cheering us all up, he will make no contribution.

For Mr Corbyn, the great cause is to be true to himself. It is an admirable and amiable characteristic. But it has the unfortunate effect of putting the Prime Minister under no real pressure, with plenty of time to block entirely predictable attacks.

On tax credits, Mr Cameron said the Government has suffered a defeat in the Lords on the issue, and in exactly three weeks’ time the Chancellor will reveal, in the Autumn Statement, what is going to be done about it. Since everyone knows tax credits are a complicated subject, it seems unreasonable to require the Prime Minister to supply an instant answer.

Mr Cameron began to tease Mr Corbyn for employing, in various capacities, a Stalinist, a Trotskyite and a Communist, and for moving the Labour Party to the Left. Having failed to take the chance to establish his authority, Mr Corbyn is becoming a subject for mockery.

This column has attracted a certain amount of adverse comment for reporting, week after week, that Mr Cameron has won PMQs. It is not, certainly, a very exciting conclusion to reach. One assumes that at some point, Mr Cameron will become over-confident, and will trip himself up by making some remark which sounds unbearably patronising, and which reads very badly in print.

But except, perhaps, by inducing a fatal outbreak of over-confidence, Mr Corbyn looks unlikely to play any part in the PM’s downfall. As for Conservative backbenchers, they today displayed a servile willingness to pose absurdly easy questions.