Holocaust Memorial Day on 27 January this year is the 75th anniversary of the liberation of the Auschwitz-Birkenau concentration camp, the moment when the world fully realised, with jaw-dropping horror, what Hitler had done to the Jews. It was an appropriate moment for Pope Francis to declare his undying opposition to anti-Semitism and his alarm at its “barbaric upsurge” in modern society, as he did this week in remarks to the Simon Wiesenthal Centre, the international body which researches Nazi war crimes and the hatred which motivated them.

Anti-Semitism has become a stain on the honour of the British Labour party though it is by no means limited to those circles. On the political left it is connected with opposition to Israeli policies towards Palestinians, where it has become confused with anti-Zionism. At its worst, it denies Israel’s very right to exist. Holocaust Memorial Day is a good time to remember the circumstances through which Israel came into being, and why denying Israel’s legitimacy – despite it being unequivocally affirmed by the United Nations – is so strongly related to anti-Semitism itself. Not wishing Israel to exist comes close to not wishing the Jews to exist.