One of the worst failings of Jeremy Corbyn is his evasiveness. If he finds a question in some way painful or awkward, he possesses to an abnormally high degree the capacity to avoid it.

This fault severely limits his effectiveness at PMQs. Today we got nothing from him about the John Worboys case, or about Brexit, or about Cambridge Analytica, or about anti-semitism – the last, an issue where his refusal over several years to confront something which needs confronting has ruined his credibility with many lifelong Labour supporters.

Nor, of course, did we get anything about economics, for Corbyn hardly ever bothers with the dismal science, even though his party will need at the next election to gain the trust of voters on the subject. Perhaps he thinks John McDonnell can take care of it.

Corbyn instead asked about mental health – a worthy topic, but not what they are talking about in the Dog and Duck, so it sounded as if he had chosen it, not on its own merits, but in order to avoid Worboys.

The fact that David Gauke, the Justice Secretary, was going to make a statement later on that subject need not have inhibited Corbyn from going on the attack. It was instead left to Zac Goldsmith (Con, Richmond Park) to refer to “this landmark decision”, and “a criminal justice system in which many of us no longer have confidence”.

Ken Clarke (Con, Rushcliffe) – the Father of the House, in which he has sat since 1970 – raised Brexit. He expressed the hope that in order to facilitate “frictionless trade”, and avoid a hard border in Ireland, the new arrangements “will resemble the existing customs union very closely indeed”.

The Prime Minister remarked that trade is “not completely frictionless today”.

Caroline Lucas (Greens, Brighton Pavilion) said the Cambridge Analytica affair “suggests there is something rotten in the state of our democracy”.

The Prime Minister agreed that “clearly the allegations are concerning”, as people should be able to have confidence in how the system works.

People should also be able to have confidence in how Corbyn works. But at PMQs, he almost never gives the appearance of having done his homework on the topics of the day. He is the laziest and most self-indulgent Leader of the Opposition in living memory.