With this creative refusal to shoot a conventional biopic (Further Beyond ends with the opening credits to a film we haven't quite seen) the film collective Desperate Optimists confirm their status as difficult blighters. But you would have trouble arguing that their tactics are without precedent.

There is something of Lawrence Stern's Tristram Shandy about the piece. Just as that 18th-century novel took endless discursions while deconstructing the form, Further Beyond refuses to settle down and be a conventional documentary. It is often frustrating. It is meant to be.

Dubliners Christine Molloy and Joe Lawlor, the two ends of Desperate Optimists’ pantomime horse, set themselves the task of making a film on Ambrose O’Higgins (near contemporary of Stern, incidentally). Born in 1720, he lived in Sligo and Meath before migrating to eventually become captain general of Chile.

But would it not make more sense to focus on his son? Bernardo O’Higgins was a key leader of the rebellion that freed Chile from Spanish colonialism. There’s your story. Right? The Optimists ask themselves that very question and can’t fully explain why they’ve decided to focus on the dad.

Not that much focusing gets done. In the opening sections, the film-makers conclude that the biopic is one of the genres that cause them unease. We then meet the two voiceover artists, one male, one female, who will narrate the film. The man worries about his billing before discussing the history of his art.

An older woman stands in for the actress Sylvia Sydney, a Bronx-born actress who was in the first film to ever use voiceover. The older woman is (or is announced to be) the Bronx- born mother of Joe Lawlor (coincidence?). So it goes.

We apologise for the unsightly parentheses, but no film this season better suits parenthetical discussion. Further Beyond packs in so many diversions that you half-expect it to groan with indigestion. There's something here about On the Waterfront. We hear musings from Zen and the Art of Motorcycle Maintenance.

It’s a small wonder the piece holds together so impressively. It’s a larger wonder that it proves to be strangely moving.