“Never again.” These were the words half-dead concentration camp survivors from the Second World War scrawled across handmade signs after their liberation. It was a message to the world denouncing the kind of apocalyptic Jew hatred that had seen millions of them wiped out at the hands of the Germans – because of their religion. And so, after the war – and the slaughter of six million Jews – we promised that “never again” would history be allowed to repeat itself, that humanity would “never again” degrade, terrorise or kill Jews the way the Germans had. “Never again” would there...