The band had one single under its belt and was on a successful tour of North America when McCullough was suddenly forced to leave, due to problems he encountered when he tried to enter Canada with the group for a scheduled show. Some accounts say it was a problem with his visa, while others indicate that controlled substances were involved -- whatever the details, he was forced to return to Ireland and was replaced by Mick Cox, who took his spot permanently. McCullough returned to London, where he helped found the band Sweeney's Men; he then jumped to the Grease Band, playing behind Joe Cocker during the latter's international breakthrough, on With a Little Help from My Friends and the tour that followed (including a performance at the Woodstock Festival), before going off on their own.
In 1972, McCullough passed an audition for Paul McCartney's new band, Wings, joining the bare-bones lineup of Denny Seiwell and Denny Laine (who were already aboard for the album Wild Life) in the first fully functional incarnation of the group. That version of Wings did play a few gigs and cut the album Red Rose Speedway, which restored McCartney (whose career had faltered somewhat with the previous album) to full critical and commercial success. Its sales were driven by the soaring romantic ballad "My Love," a hit single that gave McCullough his most visible moment on record to date, with a guitar solo that was all over AM radio in the months following its release. During the recording of the album at EMI, McCullough made an unintended contribution to another top-seller of the period when took a break -- he ended up in the adjacent studio, joining a Pink Floyd session where he made a spoken word contribution that got him onto Dark Side of the Moon. He left Wings after the one album and later turned to session work, playing on records by Marianne Faithfull, Roy Harper, Ronnie Lane, Frankie Miller, Eric Burdon, and Spooky Tooth, joining the latter on their fourth album. A hand injury in the early '80s left him sidelined for an extended period, and it wasn't until 1988 that McCullough re-emerged fully, leading his own band in Ireland. For the next decade, he confined his work exclusively to Ireland, but in the late '90s he cut a series of sessions for an album in Poland and toured the country. More recently, he has turned to songwriting and generated "Failed Christian," which was later recorded by Nick Lowe. ~ Bruce Eder, Rovi