This Metafilter post by Madamjujujive has extensive links and background on The American Folk Blues Festival 1962 - 1966, annual festival that brought some of the greatest blues acts of the USA to British audiences in the UK and put them on stage with British acts like Mick Jagger, Jimmy Page and Eric Clapton. The Youtube clips from the show are spectacular, featuring artists like Sonny Boy Williamson, Muddy Waters & Howlin' Wolf.
The American Folk Blues Festival 1962 - 1966; Vol 2; Vol 3 - The festival was an annual event with dozens of classic blues greats like Sonny Boy Williamson, Muddy Waters & Howlin' Wolf playing to appreciative UK audiences. "Attendees at Manchester in 1962, the first ever venue for the festival in Britain, included Mick Jagger, Keith Richards, Brian Jones and Jimmy Page. Subsequent attendees at the first London festivals are believed to have also included such influential musicians as Eric Burdon, Eric Clapton, and Steve Winwood. Collectively these were the primary movers in the blues explosion that would lead to the British Invasion."