‘They think they’re English because they’re born here. That means if a dog’s born in a stable it’s a horse.” That was a staple of the comedian Bernard Manning’s routine back in the 1970s. Enoch Powell had, a decade earlier, expressed the same sentiment in more refined language: “The West Indian or Asian does not, by being born in England, become an Englishman. In law he becomes a United Kingdom citizen by birth; in fact he is a West Indian or an Asian still.” Few today would laugh along with Manning or take seriously the claim that only white people...