What a break with the Labour Party we used to know. For all its faults, our main Left-wing party never fell for the violent revolutionary socialism that was common across Europe.

It was a party of brass bands and temperance movements and working men’s libraries, a party that aimed to build people up, not tear them down, a party that, as its long-serving general secretary Morgan Phillips once put it, owed more to Methodism than to Marxism. Until now.

How are we to explain the change? How can Jeremy Corbyn, dismissed throughout his career as too extreme to be taken seriously, now be ahead in the polls? The terrifying explanation is that he reflects a generational alteration in attitudes.

According to YouGov, a third of millennials think that George W Bush murdered more people than Stalin did, and fully 70 per cent have never heard of Mao Tse-tung, whose regime exterminated tens of millions of Chinese. One or two hard-faced Marxist ideologues see these deaths as a price worth paying for the eventual utopia.

You can’t make an omelette without breaking eggs, they say. (Setting aside the rather obvious objection that people are not eggs, there has yet to be a case where the omelette actually emerges: communist states always end up poorer as well as harsher, more divided as well as more oppressive.)

Most, though, never look at the broken eggshells. They think of communism as a textbook theory, not as a working system. They like the sound of humanism and social equality and shared ownership, and choose not to see that these things have only ever been enforced by police states. It is these rather innocent young people who make up the mass of “Oh Je-re-my Cor-byn” enthusiasts.

In death, Karl Marx became the thing he most despised: the founder of a false religion. His acolytes cling to their dogmas in defiance of all the evidence, and became if anything more fanatical after the Berlin Wall came down.

Now, another bearded prophet is intoning the old incantations and, horrifyingly, the cult is growing.