Sometimes people don’t recognise anti-Semitism for what it is, as long as the stated target is Israel. That’s why the recent expose of Corbyn accusing British “Zionists” of failing to understand English irony was so instructive – it only makes sense if the “Zionists” in question were British Jews.

I myself was the target of Corbyn’s slurs. In a video from 2010, he insinuated that I wrote the speeches of British MPs for a parliamentary debate. He couldn’t imagine that some British MPs might say something sensible of their own accord. No – it had to be a plot, part of a conspiracy with a Jew at the centre of it, echoing the dangerous and longstanding anti-Semitic obsession that behind the scenes, Jews control the world.

“Never believe anything until it’s been officially denied,” said Sir Humphrey in Yes Minister. Labour’s stream of official denials of its leader’s problem with Jews would be easier to believe if he didn’t himself have links with Holocaust deniers.