“Bob Dylan isn’t usually one for banter between songs, but tonight is an exception. It’s November 15, 1980 at San Francisco’s Warfield Theatre and he’s relating a story about a guitarist he first met in a Chicago blues club two decades previously: a skinny teenage hotshot with a towering stack of black curly hair and a dizzying arsenal of licks copped from Big Bill Broonzy and Sonny Boy Williamson. ‘He just played circles around anything I could play,’ marvels Dylan. ‘And I always remembered that.’ Dylan goes on to explain that, some years later, he was recording in New York and needed a guitar player. So he called him up. ‘Anyway,’ he concludes, ‘he played on Like A Rolling Stone and he’s here tonight. Give him a hand – Michael Bloomfield!’ The crowd roars its approval as Bloomfield, 37 years old, ambles on stage in his bedroom slippers and starts…