All around Hampstead and Belsize Park today, people are waking up to the sight of anti-Semitic graffiti; on shops, on phone boxes, even on the South Hampstead Synagogue. For the hard of thinking, putting ‘9/11’ alongside the Star of David is a theory by anti-Semites who blame Jews for the islamist fascist attack on America. Which is to say it is racism, pure and simple.

We can but speculate about who we believe to be behind the graffiti attacks, so there’s absolutely no point. The Jewish community will be horrified and, I suspect, frightened by what has happened and who can blame them?

It’s not as if we have completely forgotten what happened to Jews in World War Two, is it? Few seemed to have been taken in by the maniacs who say the holocaust never happened. And here we are, all these years later, with Jews still under attack.

The historian Simon Schama says this: “Taken together with the stabbings in New York something truly monstrous is rising from the slime.” I fear he is right. Just look at our own country. Anti-Semitism has always been associated with the far right, but in recent years, as the Labour Party has swerved to the far left, it has become an open sewer of Jew hatred. Yes, you read it right: the Labour Party. The people’s party that was always opposed to racism.

Jeremy Corbyn’s repeated refusal to apologise for anti-Semitism in Labour merely confirmed to many people, including the vast majority of Jews in the land, that there were major problems. It added to concerns from Jews that its leader and a significant number of Labour members were anti-Semitic. I am not saying that Corbyn is an anti-Semite because I honestly don’t know, but his behaviour in refusing to apologise, his inadequate response to anti-Semitism in the party and his miserable history of supporting middle eastern terrorist organisations, some of which oppose the very existence of Israel, do make you question Corbyn’s real views.

In other words, anti-Semitism is almost mainstream, regarded by some as normal. It is one thing to legitimately criticise Israel, as it is to criticise any other country: there is nothing wrong with that. But much of what passes for criticism in terms of Jews is far more sinister. Hence today’s desperately upsetting graffiti attacks and the stabbings in New York.

Something very dangerous is happening. This is a warning from history. And we need to stop it.