Donald Macintyre's Sketch: Over-earnest schoolmaster Jeremy Corbyn raises the tone

For a man who was only a week ago described by the Prime Minister as “security-threatening, terrorist-sympathising, Britain-hating”, Jeremy Corbyn was restraint itself in his dealings with David Cameron, less crazed extremist sociopath than patient, if slightly over-earnest, schoolmaster coaching a remedial class. “The Prime Minister is doing his best, and I admire that,” he actually said at one point, with only the faintest tinge of sarcasm.

Strangely, the most left-wing Labour leader since George Lansbury is also - so far - the politest. If with an edge. So this was a quieter PMQs, partly no doubt because Labour backbennchers were mainly - and perhaps sullenly - silent when Corbyn got to his feet. But also because the his style is frustrating for Tory backbenchers used to building the famous “wall of noise”. Especially given Corbyn’s reprise of his crowd-sourcing technique of last month. After raising a heartfelt housing complaint from Matthew, he paused (no doubt deliberately) so everyone could hear the giggles opposite. “This might be funny to some members, but it’s not funny to Matthew!” Silence.

He was equally pedagogic with Cameron. Questions about real people are tricky because general Prime Ministerial policy answers never quite fit the complainant’s dire circumstances. “I say to Matthew that we are doing everything we can to get councils to build more houses, particularly affordable houses that he can buy.” (Actually Matthew would probably be content with just one.)

“It would be very nice if the Prime Minister answered the question I asked,” declared the form teacher.

Finally the Tory backbenchers had their moment. “Where we find a good Labour policy, we implement it,” Cameron said gleefully before adding, in yet another references to Labour’s having first accepted and then rejected George Osborne’s “fiscal charter” adding “Funnily enough... are implementing what was, a week ago, a Labour policy…”

At this point, amid peals of laughter from behind the Prime Minister, the Speaker orderedto stop on the grounds that he had answered the question. “Hang on a second,” the PM protested .before standing with his arms outstretched, milking the cries of “more, more” form his backbenchers like a conjuror who had just sawn a woman in half and had been preparing to move on to some Uri Geller-style cutlery bending. Noticeably however this was long after Corbyn had sat down. The Labour leader had somewhat raised the tone. How long for, no-one can yet predict.