Donald Macintyre's Sketch: Ed Balls steamed up after presenting David Cameron with a perfect birthday gift

It all started so amiably. Not only did Ed Miliband wish David Cameron a happy birthday, but both men fell over themselves to congratulate Professor Peter Higgs of boson fame for winning a Nobel Prize. And then, to borrow a term from Prof Higgs’ branch of physics, it all reverted to the Standard Model of PM’s Questions: half-truths, dodgy statistics and old quotes to show your adversary once thought the opposite of what he says now.

But with a twist! Which was that today marked the Return of the Red Peril. Cameron made fun of Ed Miliband for wanting “to live in some sort of Marxist universe”. And Miliband made fun of Cameron for thinking he did. Cameron, he said, had admitted there was “a certain amount” you could do by freezing energy prices, while George Osborne had said it “was something out of Das Kapital”. So was the freeze “a good idea or a communist plot?”, he asked. “I’ll leave the communist plots to him,” said Cameron to general Tory mirth.

At times it got a bit confusing. Cameron said it was “obvious” why Miliband “wants to talk about the cost of living: it is because he does not have an economic policy any more”. To which Miliband replied: “The Prime Minister said something very interesting: he said he does not want to talk about an economic policy; he wants to talk about the cost of living. He does not realise that an economic policy is about the cost of living.” But hang on. Cameron was saying it was Miliband who doesn’t want to talk about an economic policy, not the other way round. It was Miliband who… oh forget it.

Cameron announced he had had a “special birthday treat”, namely that Balls had said Labour’s election campaign “depended on the two of them together” because of their “experience, track record and credibility”. Cameron added triumphantly: “That is like the captain of the Titanic running on his safety record.” Good gag, though pedants will point out that since Edward John Smith went down with the ship in 1912 he didn’t do much running of any sort after that.

Finally, Balls raised a “point of order” about Cameron’s claim that all married couples on the basic tax rate would get his new allowance. Something new: a Balls/Cameron head to head! “I stand up for marriage, even if the right hon. gentleman wants to talk it down”, the PM declared, receiving a slap on the back from Osborne as he left, despite being technically in the wrong. This hint that Labour despises the institution as bourgeois seemed a bit harsh since even Marx – like Balls – was happily married.

But anyway, surely Marx would be spinning in his grave – which, the Daily Mail has pointed out with sinister overtones, is in Highgate Cemetery, like that of Miliband’s late father – at what he would see as the outrageous notion that the irretrievably social democratic Labour Party was his natural heir.