When the Fat Lady Sings, everyone is primed to chortle, even if she is Montserrat Caballé and doing it wonderfully well. Hergé’s cartoon creation of Bianca Castafiore embodies the type: with her flaxen plaits and heaving embonpoint, she is a ridiculously bad fit for the simpering virginal heroine of Gounod’s Faust, particularly when carolling her Jewel Song at such a pitch that an agonised Tintin and Captain Haddock are forced to cover their ears.