The party leader fails to control bigotry because he sees Israel as the Middle East’s worst offender

Anti-Semitism is like a virus. It can spread fast among a population. The history of continental Europe shows that otherwise kindly and rational people can be encouraged to start spouting odious prejudice.

Even in this country we have seen episodes in the past 1,000 years when that virus has raged through society, with catastrophic results; and we have also seen how it can then go dormant. The spores of hate will wait beneath the floorboards. Then all of a sudden, one day, the disease can flare up – but not spontaneously, not without help.

When anti-Semitism takes hold again, it is because that virus has been potentiated by the stupidity or opportunism of politicians. When you look at what is happening in the Labour Party today – the real fear and distress of Margaret Hodge MP – it is clear that something is going badly wrong.

Last week, all three main Jewish papers cleared their front pages for a joint editorial claiming that Jeremy Corbyn presented an “existential threat” to the Jewish community in Britain. At the very least there has been a disastrous breakdown of trust; and no wonder.