Don Barry Mason was the founder of the Psychedelic Shamanistic Institute (PSI), which other member that's Welsh, that died on 10 April 2016?
Don Barry Mason:  Associates of PSI include: Mathew Atha, Colin Angus, Brian Barritt, Michael Carmichael, Fraser Clark, Paul Devereux, the late John Entwistle, Paul Flynn MP, Ben Ganly, Lee Harris, Mike Jay, Howard Marks, Dr John Marks, Jonathan Ott, Dr Russell Newcombe, Richard Rudgley and Youth. Howard Marks: Dennis Howard Marks (13 August 1945 – 10 April 2016) was a Welsh drug smuggler and author who achieved notoriety as an international cannabis smuggler through high-profile court cases.
Dennis Howard Marks