The initial incarnation of Fleetwood Mac performed its first gig in August 1967 at the seventh annual Windsor Jazz and Blues Festival, playing a Chicago-style blues. McVie, initially hesitant to commit, was later prompted to leave the Bluesbreakers and join Fleetwood Mac full-time when the former adopted a horns section with which he disagreed. He replaced the initial bassist, Bob Brunning. McVie, Fleetwood, Green and guitarist Jeremy Spencer thus formed the first fixed line-up of Fleetwood Mac.  The band's first album, Peter Green's Fleetwood Mac, was released in 1968, and the band toured the United States for the first time, though Green was reluctant to do so for fear of gun crime. Upon their return, they recorded a second album, Mr. Wonderful under simply "Fleetwood Mac" with Green's name dropped. A guest musician on the album, Christine Perfect, became close with the group and she and McVie were married in 1968. A third guitarist, Danny Kirwan, was also added to the line-up. Despite the success of their third album, Then Play On, and a string of hit singles including "Albatross" and "Man of the World", Green himself drifted away from the band, struggling both creatively and with increasing use of LSD. He later joined a Christian religious group.  Fleetwood himself later remarked on the growing stature of Green's difficulties: "I think there is certainly some credence given to the idea that Peter's condition could in some way be blamed on a bad acid trip he had in Germany ... I don't think it did him much good." He also recalled in 1995 that "Peter basically ceased to see the light with Fleetwood Mac and had aspirations of playing for nothing in strange places--none of which really happened. He made several interesting albums after he left, then basically took a left turn in terms of his psyche. He pulled out of the mainstream and chose to stay at home. He doesn't play much anymore, which is certainly a shame, because he's my mentor, and he's the reason that Fleetwood Mac became what we became."

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