W rapped in a vast white sheet, Rosalía is telling the audience a story about her youthful dreams of performing in London, undaunted by the fact that her English is, as she puts it “a little bit rat-a-tah”. It turns out her real ambition was to sing at the Royal Albert Hall – “which I’ve never done” – but no matter: “I have sold out two nights at the O2!” she cries triumphantly. “Crazy, crazy,” she adds, shaking her head. You can understand the Catalan singer’s surprise. We are supposed to live in a hopelessly risk-averse era for pop, where what audiences are deemed to want is more of the same.…