Slender limbs, intense eyes, and dressed entirely in black: if it wasn’t for the straightened blonde hair, Carla Bley could pass for a jazz Patti Smith. She is also, of course, one of the genre’s most acclaimed composer-arrangers, and her return to London is much anticipated. Before she plays a note, the septuagenarian Californian walks awkwardly, defiantly, to a microphone at the front of the stage.