How very English to turn a debate about war and peace into an argument about manners. Opposition MPs called on David Cameron to apologise for urging the Tories not to vote with “Jeremy Corbyn and a bunch of terrorist sympathisers”.

The Prime Minister had not said this in the Chamber, but at a meeting of Tory backbenchers, and he began his speech by insisting that “I respect people who come to a different view” from himself: the question before the House was not whether to fight terrorism, but how.

Cameron then took numerous interventions from Labour and SNP MPs who wanted him to say sorry for his “disgusting” reference to “a bunch of terrorist sympathisers”. Since he had made it clear that he was not going to apologise, these confected expressions of indignation became more and more pointless.

There is something rather rude about refusing to accept someone’s assurance that he will respect you even if you do not vote with him. But feelings were running high, and Cameron’s opponents were desperate to find some way of getting at him.

On the substance of the issue, which was whether or not to bomb ISIS in Syria as well as Iraq, Cameron asked: “Do we wait for perfection?” He said he was not pretending the 70,000 troops in Syria who might support us “are somehow ideal partners”.

Here was a convincing politics of imperfection. The Prime Minister did not claim, as Tony Blair might have been tempted to do, that we were engaged in some high moral attempt to bring democracy to Syria. Cameron just thought it would on balance be better to join two of our closest allies, the French and the Americans, in making these air strikes, than to sit things out.

How would Corbyn respond? He started, unfortunately, by calling on Cameron to apologise for the “terrorist sympathisers” remark. Coming from Corbyn, that sounded shameless as well as pointless. Has he not shown, at various points, sympathy for the IRA and various other terrorist organisations?

Corbyn took quite a number of interventions, some from his own side, and did not deal with them very happily. John Woodcock (Lab, Barrow and Furness) asked him if he would remove air protection from the Kurds in Iraq. Corbyn avoided answering the question, and decided to take no more interventions.

But David Burrowes (Con, Enfield Southgate) was so keen to get in that Corbyn at length allowed him to do so. Burrowes reminded the House that on 26th September 2014, Corbyn had voted against air strikes in Iraq, and asked if the Labour leader was still against such action.

Corbyn made some pious remarks about radicalisation, but refused to say what he now thinks about air strikes in Iraq. Jacob Rees-Mogg (Con, North-East Somerset) used a point of order to put the Iraq question again. There were cries of “answer”, but Corbyn refused to answer.

He must have known the question of whether he supports bombing in Iraq would come up, yet he had nothing to say in response to it. This was incompetence of a high order.

As a backbencher, one can, if one wishes, strike attitudes and refuse to think through their implications. But to take that approach as Leader of the Opposition is stupid, for one is bound to end up looking ridiculous. Never mind whether Corbyn sympathises with terrorists. Today’s shambles shows he is not bright enough to be Leader of the Opposition.