Weston was recruited into the Fleetwood Mac line-up in late 1972 as replacement for the recently-sacked guitarist Danny Kirwan. Together with fellow new band member, vocalist Dave Walker, Fleetwood Mac recorded the Penguin album in January 1973. Weston’s contribution to the album was mainly as a lead guitarist alongside Bob Welch, but he stood out thanks to his slide guitar, especially on “Remember Me”, and his accomplished harmonica and banjo playing. He also sang with Christine McVie on the song “Did You Ever Love Me”, and wrote the instrumental that closed the album, “Caught in the Rain”.
Later in 1973 Dave Walker was asked to leave the band, and the remaining members of Fleetwood Mac recorded their next album, Mystery to Me. Weston contributed more solid guitar work, for example his slide intro on “Why”, a song for which he felt he did not receive the credit he deserved. He also co-wrote one track, “Forever”, with Welch and John McVie.
During a tour of the US in late 1973, when the band were beginning to gel particularly well onstage, it emerged that Weston had been having an affair with Mick Fleetwood’s wife, Jenny Boyd. Fleetwood tried to carry on regardless, but eventually after a gig in Nebraska, he had had enough. Weston was fired and the rest of the tour was cancelled, the band members each travelling to a different part of the world to gather their thoughts. It was this situation which gave rise to the “Bogus Fleetwood Mac” affair in which manager Clifford Davis recruited a new group of musicians, passed them off as Fleetwood Mac, and sent them out to complete the tour. Although the fake band were quickly rumbled by fans, the subsequent legal battle lasted years, preventing Fleetwood Mac from recording.
Arguably Bob Weston had a very big effect on the Fleetwood Mac story, perhaps greater than his musical legacy, since it was this turmoil which strongly contributed to Welch’s disenchantment with life in Fleetwood Mac, and his departure in late 1974 paved the way for the arrival of Lindsey Buckingham and Stevie Nicks, who would help the band on to superstar status.