Heard the one about Ronnie Biggs's latest release? No, the 75-year-old Great Train Robber has not been let out of Belmarsh, despite a bid by his legal team for a judicial review. Instead, a CD inspired by the one-time fugitive is about to be made available - 30 years after it was recorded.

Biggs's shoutings as guest vocalist for the Sex Pistols are part of rock history, but until now his work in progressive jazz has been kept quiet. The dalliance dates back to 1974, before the Pistols were formed and shortly after Biggs turned up in Rio.

At the time, Brazil was a dictatorship. Biggs was introduced to an American bass player, Bruce Henry, who turned the Briton into an unlikely muse. "To me, Ronnie symbolised a rupture from the restraining chains of politics, police, short hair and suits," he says. "I think Ronnie and I shared an attitude - he still had this adolescent restlessness, and was seeking new forms of expression, a bit more tingle in his life."

Henry gathered together some talented local musicians with the idea of writing a soundtrack to Biggs's life, just in case it was ever made into a film. The film never happened, but the soundtrack did. Ronnie never sang, although he is credited as "inspiration and storyteller".

Henry, who has played with Herbie Hancock and Gilberto Gil, remembers that Biggs would sit down with the musicians and tell them anecdotes about his life. "When we went into the studio to record, we had the whole album pretty well defined, but we left a lot of room for individual inspiration - as was the style in 1974."

The sessions were never released, nor was the music ever performed live. It was only recently that Henry rediscovered the original tapes and decided to repackage them as Mailbag Blues: Ronnie Biggs's Story.

The music is a fusion of experimental jazz, blues and funk, with echoes of Brazilian styles such as tropicalia and bossa nova. Mailbag Blues offers an unexpected perspec-tive on an incredibly creative period for Brazilian music - as well as surprising us with a hidden nugget from Ronnie Biggs's life story.