A shudder, whether of revulsion or mere embarrassment, tends to precede rational reflection on the topic of immigration, and as often as not replaces it entirely. Xenophobes fear the alien in their midst: the smell of strange cuisines, the presence of other races and the outlandish appearance of foreign garb. Liberals, on the other hand, bristle in reaction to these very same prejudices – which, to be fair, make even many Conservatives squirm. Ukip supporters, described by David Cameron as “closet racists”, experience a kind of double shudder at both immigrants and domestic bigots. Ukip voters, so the jibe runs, would like to vote BNP, but shop at M&S; a genteel bashfulness and net-curtain propriety constraining cruder expressions of anti-immigrant sentiment.