The best one can say about Johnson is there are no grounds to fear him. Former mistresses and colleagues pay him a tribute of sorts by remaining loyal and affectionate, even after he has exploited them. He may be a chancer, but he is an entertaining and charming chancer without a trace of the sinister in him.

One cannot say the same about his opponent. In the 2008 mayoral campaign I went to a press conference where Livingstone had lined up speaker after speaker to say that Johnson and the Conservative-supporting London Evening Standard were engaging in racism when they levelled accusations of corruption against a black Livingstone aide.

"Are you saying that Boris Johnson is a racist?" we asked. Livingstone thought for a moment. He lacked the nerve to accuse Johnson of racism directly — even he knew that Johnson was free of that vice. Instead, his face fixed itself into a mask of pained piety as he constructed a sly reply. Although he could not know what went on in Johnson's mind, he said, he could state with confidence that the Johnson campaign appealed to racists.

I will use the same form of words to describe Livingstone's attitude towards Jews. I cannot say that he is an anti-Semite — for how can I know what animates his mind? But if you were an anti-Semite he would be your preferred candidate. I hope that readers who trouble to buy You Can't Say That (a self-pitying and self-dramatising title for Livingstone to fix on, by the way, when no one has ever stopped him saying anything) will notice that he is a politician with Jews on the brain. At one point Livingstone stops the narrative for a long and barely comprehensible discussion of the ramblings of an obscure American Marxist-Leninist from the 1980s. Livingstone hurries him on to the stage because he carried on a tradition the Stalinists began of alleging that Jews collaborated with the Nazis so they might break free from the glorious future Communism offered and use Nazi persecution to justify the creation of Israel.