It’s appropriate that this absorbing, tender documentary has been driven by a surge of fan loyalty and love. A grassroots Kickstarter campaign funded it, and utter devotion and commitment from film-maker Steve Sullivan has found order in the chaos of VHS tapes, cardboard cutouts, notebooks, costumes, memorabilia and inspired zine artwork. His subject is Chris Sievey, the talented Manchester guitarist and songwriter, whose strange destiny it was in the 80s to find fame – or cult status – for a wacky comedy character he created in an idle moment called Frank Sidebottom that he played on stage with a big papier-mache head.

The character took off. Chris’s pop dreams were in effect abandoned because Frank was a real success (though of a much more marginal sort than the success Chris was yearning for). So he became passionate about Frank, subordinating his own identity and existence to this bizarre figure, like Peter Parker with Spider-Man. Frank became a semi-star with an utterly fanatical but small and unmonetisable following; he achieved some success on children’s TV and local TV, but something in that strange, unmoving face and the bottled-up nasal voice inside was resistant to a real breakthrough.

In fact, Chris/Frank has already gained a type of movie immortality with a film inspired by his life, Frank (2014), co-written by Frank’s former band member Jon Ronson, who is interviewed here.

Sullivan’s documentary sheds more light on one central question: was Frank Sidebottom a creation of pure surrealist/performance-art genius? Or was he a creative cul-de-sac, a semi-funny piece of strangeness being laughed at, not with, by his raucous fans? Sullivan’s film inclines towards the former. So do I. If nothing else, Sievey was a tremendous comicbook artist whose drawings are rightly adored.

Sievey died early, of cancer, at the age of 54. More heartbreakingly still, his son Harry – a wonderful interviewee here – died in a road accident after the film was made. Can we posthumously confer on Chris Sievey the title of national treasure?