Until recently, Balfour’s fears would have appeared absurd. In the years between the wars, Britain remained untainted by the anti-Semitic movements ravaging the Continent. When Oswald Mosley, leader of the British Union of Fascists, took up anti-Semitism in the 1930s, he became a political pariah. But hostility to Israel has now morphed into anti-Semitism in countries hitherto relatively free of it; Britain, Australia, Canada and the United States. In Britain it re-appeared, not amongst ill-educated inadequates of the sort who supported Mosley, but first in the Labour Party under Jeremy Corbyn, and then in our top universities, amongst our future...