The 5000 Spirits album went to Number One in the UK folk chart. Hangman's reached the top 5 in theBritish album charts and was nominated for a Grammy in the USA.
By 1968, the group were playing (and filling) venues like London’s Royal Festival Hall and Royal Albert Hall, and picking up gigs at open-air festivals and prestigious Stateside rock venues including both of Bill Graham’s Fillmore auditoriums.
Boyd made the mistake of introducing them to David Simons (aka "Rex Rakish” from Jim Kweskin's Jug Band) after an appearance at the Fillmore East in New York and remarking that he’d straightened his act up considerably. The change was attributed to Scientology, and when Boyd left them to talk Simons persuaded them to enrol in the cult.
The band's support for Scientology has been used to explain what many fans saw as a gradual decline in the quality of their work, but 1968’s other album Wee Tam and The Big Huge was recorded before the US trip and while it wasn’t quite as groundbreaking as its two predecessors they had to slow down eventually.
If you were looking for a non-Scientology explanation for a perceived decline you probably don’t need to look much further than communal living arrangements at a farmhouse in Pembrokeshire, where mixed media experiments with Malcolm Le Maistre and David Medalla's Exploding Galaxy troupe added new influences, and, arguably, diluted the blend of influences. The Inquisitive Reader can find evidence in a film about the ISB, Be Glad For the Song Has No Ending. A mixture of documentary footage and a fantasy sequence called The Pirate and the Crystal Ball, it was shot for the BBC TV arts programme Omnibus, and subsequently reissued on video and DVD.
The next couple of albums, 1969’s Changing Horses and 1970’s I Looked Up were either marking time or gradually slipping, depending on where you sat. A new communal base back in Scotland (at Glen Row near Innerleithen) and continued experimentation with exotic instruments, colourful stage costumes and surreal theatrical sketches and dancers from the Stone Monkey troupe came to a peak with U, Williamson’s multi-media event at London's Roundhouse, followed by a double album containing the songs from the stage show.