David Cameron today defeated Michael Foot, Leader of the Labour Party from 1980-83. He also trounced Neil Kinnock, who led Labour from 1983-92. It was something of a surprise that the Prime Minister did not attempt to walk all over Keir Hardie, the first Labour leader, but perhaps not enough people remember Hardie.

The Prime Minister made clear that he intends to defeat Ed Miliband, who has led Labour since 2010, by portraying him as a pre-Blairite socialist: an Old Labour figure who “is painting himself into the red corner” and has learned nothing about how the economy works. So when Miliband attacked the privatisation of the Post Office as “a rip-off of the taxpayer” from which privileged financiers “made a killing”, Cameron retorted: “These are exactly the arguments that Michael Foot made about the privatisation of the National Freight Corporation…as Neil Kinnock made about British Telecom and British Airways.”

And in a carefully prepared passage, Cameron said that over Easter he had been studying Labour’s list of candidates and saw that “son of Kinnock is coming here, son of Straw wants to get here, son of Prescott wants to come here. It’s the same families with the same message.”

How shameless of a Tory Prime Minister to pour such scorn on the hereditary principle. Who was Winston Churchill’s father? Lord Randolph Churchill, Chancellor of the Exchequer. It has never been forbidden in British politics to draw inspiration from one’s parents, and to learn from them something about the practice of politics. It is a very good thing that not every MP is a completely new man or woman, who brings no inherited understanding of what a parliamentary career entails.

The Speaker, John Bercow, intervened to halt another over-long passage in which the Prime Minister was talking about the Labour Party rather than about the Government’s record. Cameron protested that he had not finished, to which Bercow retorted that “the Prime Minister has finished, and he can take it from me that he’s finished”.

It is unfortunate that on these occasions, the Speaker looks and sounds like a petulant schoolmaster who has lost the respect of the class. He has no natural air of authority, but on the merits of the question, Bercow was right. The Prime Minister cannot be allowed to engaged in prolonged diversions in which he sets out to describe the Labour Party as he would like it to be.

Not that Miliband has yet managed to do very much to define a post-Blairite socialism. Until he does, Cameron the caricaturist can continue to win these encounters by drawing him as a latter-day Foot or Kinnock.