The early British Invasion groups revered the Black Bluesmen and European tours were arranged to give them exposure to a wider audience and give them their due. From Perfect Sound Forever is this.
The Web Is Woven Tightly
The standard story most commonly told about Sonny Boy Williamson II emerged primarily from a series of interviews he did, mostly with Blues Unlimited in 1963-65 in Europe. I have yet to find evidence of a substantive original interview of Sonny Boy by an American blues writer. He is referenced everywhere only in the most respectful but superficial terms with little follow-up research.
Sonny Boy, at the time, was clearly the star of the 1963 and 1964 American Negro (Folk) Blues Festivals. Along with Willie Dixon (the talent coordinator) and Horst Lippman (the promoter), he toured Europe during those two autumns along with Muddy Waters, Howlin' Wolf, Lightnin' Hopkins, Lonnie Johnson, Sleepy John Estes, Big Joe Williams, Otis Spann and a select cast of blues legends playing their most brilliant music with each other. Sonny Boy Williamson was the acknowledged and revered star of the tour. When he returned to Britain to tour the college circuit on his own with a very young Eric Clapton and the Yardbirds hanging on for dear life as his backup band, he extended his legend.
He recorded not only with his fellow legends Memphis Slim, Hubert Sumlin and Matt "Guitar" Murphy but also with the Clapton-era Yardbirds, the Animals and, on his final day in England, Jimmy Page, Brian Auger & The Trinity and two jazz sax players! He returned home to die a month later in his home of Helena Arkansas but not before returning to the jukes and his beloved King Biscuit Time radio show and a final jam with Levon & The Hawks (yes, the folks who became The Band) who told the story in a memorable interview segment of "The Last Waltz." movie. Sonny Boy died in sleep in his humble apartment on May 25, 1965. The rumor is that, had he lived but four months longer, he would have been a member of The Band (then The Hawks) when they joined Bob Dylan. One can only wonder if Dylan would have been cheered rather than booed in 1966 if he had Sonny Boy with him on that tour. The mind boggles.