By far the best line today came from Jonathan Reynolds (Lab, Stalybridge and Hyde), who began his remarks to the Prime Minister: “As the new leader of the anti-austerity movement in Oxfordshire…”

That produced a deep prime ministerial blush, and for the first time in over half an hour, a few moments of laughter on the Labour benches. Being led by Jeremy Corbyn is not turning out to be a happy experience for them.

Nor is it turning out to be a happy experience for Mr Corbyn. His manner at the Dispatch Box is that of a new boy who has failed to settle down, and is uneasily aware that the other boys, and also the girls, are just waiting for a chance to tell him how utterly  and completely useless he is, especially on the question of the moment, which after the Paris attacks is national security.

Mr Corbyn proceeded with caution. He took cover behind platitudinous expressions of regret. But Mr Cameron dragged him forth and told him: “We can’t dodge forever the question of how to degrade ISIL both in Iraq and in Syria.”

The Prime Minister added that “when confronted by a Kalashnikov-wielding terrorist”, the last thing the police want is guidance from someone who “isn’t sure what the reaction should be”: a direct attack on Mr Corbyn’s equivocations on that subject.

What could Mr Corbyn do? He was helpless, and worse than that, he was dull. For the first few weeks of  his leadership, the House heard him with respect: there was general recognition that his new way of doing PMQs deserved a respectful trial.

The style is acceptable: the lack of substance is not.  The horrors of Paris have been a disaster for him. He has failed to speak even for his own MPs, let alone for the wider nation. Here is a Leader of the Opposition who is able neither to oppose the Prime Minister, nor to supply worthwhile bipartisan support at a time of crisis.

In the Commons press gallery, journalists were more interested in the offensive remark made by Ken Livingstone about mental illness. Mr Livingstone is nowadays seldom often the airwaves, and is clearly loving the attention. He acts as Mr Corbyn’s advocate, but on this occasion had behaved outrageously, and was refusing to make the immediate apology which was called for.

Mr Corbyn, it appears, cannot even control Mr Livingstone, and is already regarded with a mixture of anger and derision by the majority of Labour MPs, whose electoral hopes he is in the process of wrecking. Nor can the Labour leader retrieve his fortunes by scoring off Mr Cameron. This column predicts that within a few months, Mr Corbyn will have been forced to resign from a role which he is palpably incapable of performing.