The V&A’s Diva begins, like all exhibitions staged in its costume galleries, in sepulchral gloom. Even as the ears fill with the sound of a beautiful voice – visitors are given headsets, and first up on the soundtrack is Maria Callas, in Bellini’s Norma, recorded at La Scala in 1954 – the eyes struggle to adjust to the dark. In a way, it’s perfect. This show, sold out on the day I visited, is as much about performance as it is about pan-sticked individuals and their healthy egos. The space has, if you like, been transformed into a kind of theatre, the house lights down, the curtain about to go up. Squinting in the murk, you prepare yourself for drama: for sequined headdresses and feather boas, for dressing room riders as long as your arm.