It appears that Cyril did some session work for a few UA acts at the time, but it’s possible that this was the only appearance that actually got a release; the others not getting any further than the acetate stage. It was recorded at Olympic studios and Cyril played on the B side as well, but the trademark Groovies sound is much less apparent there. Cyril used a blue fender mustang tuned to open G and a brass slide and set the pickup switches to sound like Ry Cooder.... It appears that they just wanted some slide guitar and "there weren't that many guys out there that played slide" so he got the job.
Not quite sure how this remained undocumented for so long, but here it is in all its 1972 crushed velvet and studded leather glory.
Thanks to Don and Cyril for the info.