Gordon briefly joined King Crimson in 1970 after appearing as a guest vocalist on In The Wake Of Poseidon singing Cadence & Cascade.
He was asked to join the band full-time in the summer of that year and provided bass and vocals on Lizard, the last album King Crimson recorded at Wessex Studios.
The experience was not a happy one for Gordon and he bitterly regretted his decision to join.
I think he regretted joining when the verbal agreement for future royalties was not acknowledged after the fact. It was over nonpayment of money I believe.
Anyway he was in a very important lineup of the band however brief.