As Labour leader, Corbyn was always going to face questions about his attitude to Israel; for many activists in his section of the left, Zionism is a form of Western colonialism comparable to apartheid. Notably, the definition of anti-Semitism that Corbyn refused to accept last year focused on Israel. (It stated that it was unacceptable to compare Israel’s actions to those of the Nazis, accuse Jewish citizens of “divided loyalties,” or call the existence of Israel a racist endeavour.) The saga revealed that many Britons have no idea that anti-Semitism does not comprise only abuse hurled at Jewish people, and little appreciation of the vital distinction between, say, criticism of illegal settlement-building and suggestions that Israel has no right to exist at all.

Disproportionate hatred of Israel is one strand of left-wing anti-Semitism. The other is the conspiracist turn, turbocharged by social media, which gains succor from attacks on “the elite,” “the 1 percent,” “the mainstream media,” and “billionaires.” Corbyn has made such attacks a key part of Labour’s appeal, adopting the slogan “For the many, not the few.” The trouble is that while all of these are superficially innocent phrases—as well as useful ways of describing a world in which wealth and opportunities are unequally distributed—it is clear that some supporters hear them as a dog whistle. Jews have long been accused of running shadowy cabals: References to the Bilderberg Group, the Rothschilds, and George Soros are staples of online conspiracy theories. This tendency intersects with the anti-colonialist view of Israel, Mike Katz, the chair of the Jewish Labour Movement, which represents Jewish socialists, told me. “In the way people talk about ‘who’s bankrolling Zionists?’ Jews have always been accused of having divided loyalty,” he said. “Prior to Israel, it was some shadowy world government.”

Over time, these concerns have built up.