Many of us will have done our regular security duty over the chagim. Thank God, that duty proved to be entirely precautionary. But not in Halle, where, on Yom Kippur, a 27-year-old, far-right extremist murdered two people outside the synagogue where the congregants were gathered.

Those deaths show how vital security is for Jews everywhere. Were it not for the synagogue’s locked door, which even the murderer’s explosives did not breach, the death toll would have been far worse. Security experts have rightly focused in recent years on the threat posed by Islamist terrorists. But it is now clear that the threat from the far-right is no less dangerous.

The murder last October of 11 worshippers at the Tree of Life shul in Pittsburgh was the worst ever massacre of Jews in America. And there is plentiful evidence of links, even if only ideological, between the murderers in Halle and Pittsburgh — and others.

Both before his killings and during his live stream, the Halle perpetrator spoke of how immigration and feminism were imperilling the white race, and that “the root of all these problems is the Jew.”

He also wrote of how, “If I fail and die but kill a single Jew, it was worth it”. The Pittsburgh killer had similarly ranted online about how Jews had brought “evil Muslims” into the US.

In a sense, it does not matter whether they, and the likes of Anders Breivik, were conspirators or copy-cats, because the effect is much the same. Such antisemitic hatred is commonplace on mainstream social media — but it also has a home on platforms such as 8chan. And it is not going away.

How we respond to it will define our community for the coming decades.