I n 1968, Taj Mahal was onstage at the Whisky a Go Go in Los Angeles when he looked out and realised he was performing to a who’s who of British rock music. “Three of the Stones were dancing, along with three of The Animals,” he remembers. “Eric Clapton was in the back of the room. There was a current going back and forth.” The young stars of the British Invasion all borrowed heavily from the blues, and were intoxicated by Mahal’s thrillingly electrified version of American roots music. In turn, the then 26-year-old had grown up in the States tuning in to UK radio shows. After his set, he approached Mick Jagger and asked him to let him know if there was ever an opportunity for his band to play in England. “Three months later, they sent us eight first class round-trip tickets,” remembers Mahal.…