Lars von Trier is an unusual director, in that he makes films of massive emotional intensity, and yet also appears interested in formal innovation for its own sake: the Dogme manifesto, of which he was co-author, suggested that films should be made according to certain rules, partly for the expected benefits of following them, but also for the benefits of simply being constrained (a philosophy resembling that of Georges Perec and the Oulipop group of novelists). In some ways, 'The Five Obstructions' is both the perfect demonstration of this attitude, and also his strangest film yet. Jorgen Leth is a director who made, in 1967, von Trier's favourite film, an innovative (but arguably cold) short called 'The Perfect Human'; in 'The Five Obstructions', Leth agrees to remake this film in five different ways, subject to constraints imposed by von Trier. The story of his doing so, along with excerpts from all six films, comprises this one. It's the ultimate recursive project, a "making-of" documentary with itself as both subject and object, an effect enhanced by the way that each film becomes a commentary on, and an extension of, its predecessors. von Trier does not dare, however, to suggest he can improve on the original; on the contrary, he professes to hope that his obstructions will force Leth to make a bad film, and therefore reveal something more of his own emotions than have hitherto been shown. In this, however, he fails. 'The Five Obstructions' becomes a film-making masterclass, as Leth continually finds something new to say in spite of the increasing restrictions against him saying anything; his natural inventiveness, and skill, make you want to see the films he has chosen to make for himself. von Trier, by contrast, appears as a fool, although as the resulting documentary is his creation, he is maybe not as foolish as he appears. Indeed, there's almost certainly an unavoidable level of artifice in the apparently "real" scenes where the two men talk, each are too skilled as film-makers to be wholly unaware of what they are doing. But there does seem to be a real human story, as Leth's enthusiasm for his task, and for life itself, is driven upwards by the series of apparently insane challenges with which he is encumbered. It's an odd film for anyone to make, but maybe proves von Trier's point; for what stands above the contrivance is pure gold.