Dir: Lars von Trier, Jorgen Leth. Denmark. 2003. 91 mins.

This two hander by the Great Dane, Lars Von Trier, and his older colleague and compatriot Jorgen Leth, is one of the most thought-provoking slices of cinema we are likely to see this year. It is in many ways a more honest film than Dogville, Von Trier's big American drama, which previewed at Cannes, if only because in this oddball documentary von Trier the Machiavellian manipulator of actors and spectators is not hiding behind the camera, but up there on the screen. Don't expect to see it at your local multiplex; but the von Trier moniker and the sheer kookiness of the film's premise should make this a more saleable arthouse contender than might be expected; word of mouth and critical buzz should upgrade it from film club to commercial indie circuits.

In 1967, documentary director Leth made a 12-minute black-and-white short called The Perfect Human, which has since become a cult rarity (von Trier claims to have watched it more than twenty times). Imagine David Byrne scripting and directing an educational short about human behaviour and you come close to the flavour of this little curio. It shows us a man in formal dress performing a series of simple, unconnected actions - shaving, eating, dancing, falling to the ground - while a voice-off narrator asks questions to which there are no answers: What is the man doing' What is he thinking' Is he three cards short of a full deck'- that sort of thing.

Von Trier's idea is to get Leth to remake The Perfect Human five times. Each time he will raise an Obstruction, consisting of one or more technical shackles which Leth has to overcome. Discussions between Leth and von Trier, which mostly take place in the Zentropa offices in Copenhagen, are sandwiched in between outtakes from Leth's original film and the five finished remakes. In a way, these conversations - often uncomfortable, and sometimes hilarious - constitute the most compelling part of the film. Take the first obstruction: von Trier orders Leth to shoot the film in Cuba (Leth happens to be smoking a cigar at the time), without a set, and with no sequence lasting more than12 frames in the final edit (that's half a second). Leth, a meticulous and rather reserved cineaste, is too honourable and too committed to the game to refuse point-blank. But his face speaks a thousand words - three of which are expressed in an aside to the camera after the meeting: "He's completely mad!".

When he tests Leth's moral probity by asking him to shoot a banquet scene in the most miserable slum in Bombay, we can almost see von Trier's horns, imagine the pitchfork - and the infernal side of his nature is only emphasised by that permanent, unsettling grin, that pulling-wings-off-butterflies expression. So many ideas are being thrown up here that it's difficult to keep track: the master-pupil relationship is being subverted, there are heavy religious overtones of sin, confession and penance; issues of artistic freedom and the necessity of limitations are probed (Leth's punishment for not having strictly observed the second obstruction is to do the third remake without any rules at all - a challenge which he calls "diabolical").

And in between these power-plays come Leth's five films; beautifully shot, just occasionally dull and inaccessible, they would be arid art cinema exercises without their frame. But from the frame they gain in stature. This is an essential film for anyone with even half an interest in cinema.

Prod co: Zentropa Real
Co-prods: Wajnbrosse Productions, Almaz Film Productions, Panic Productions
Int'l sales: Trust Film Sales
Prod: Carsten Holst
Exec co-prods: Peter Aalbaek Jensen, Vibeke Windelov, Marc-Henri Wajnberg, Gerald Morin, Nicole Mora
Cinematography: Dan Holmberg
Ed: Camilla Skousen, Morten Hojberg
Main cast: Lars von Trier, Jorgen Leth, Jacqueline Arenal, Daniel Henandez Rodriguez, Patrick Bauchau, Alexandra Vandernoot