Georg Trump’s Forum I in use for June 1, 1974, a live album of songs performed at the Rainbow Theatre in London on said date. “The album is officially attributed to Kevin Ayers, John Cale, Brian Eno and Nico, although other well-known musicians, including Mike Oldfield, Robert Wyatt and Ollie Halsall, also contributed to the concert. […] The cover photograph was taken by Mick Rock.” –Wikipedia
From the liner notes:
Kevin Ayers came back from the Rhône Valley to play the Rainbow, and decided to invite some guests to assist the festivities. He first invited his friend Nico, and through her contacted John Cale, another member of the original Velvet Underground. John, in London to record an album of his own, brought along Eno, who was greatly pleased to be working with some of his heroes (and heroine). Kevin asked Robert Wyatt, with whom he played in the Soft Machine during 1967–8, and Mike Oldfield – who, when he was 17, had been a vital member of Ayers’ fascinating 1970 band, The Whole World. Behind them where the Soporifics, Kevin’s new touring outfit, and three nice lady singers. After a week’s rehearsal at the Walpole Picture Theatre in Ealing they were ready for the Rainbow, where 3,000 souls awaited them behind “sold out” notices which had gone up days before. It was an extraordinary concert, a rare pleasure for those who’d followed the performers’ various careers through the past ten years.