The British tend to view Donald Trump as an unprecedented only-in-America freak. Self-glorifying libertine billionaire turning his media ingenuity and unbounded reserves of cunning ignorance into a nativist political career. Racism and misogyny lightly disguised as heroic candour. The strongman allure, and the tendency of opponents to dismiss him as a buffoon. He’s the American Berlusconi. Which should serve as a warning to anyone who thinks he can’t possibly win.