Jarman's biopic brings to life the seriously eccentric philosopher Ludwig Wittgenstein: Viennese millionaire's son, schoolteacher, WWI infantry officer, hospital porter, gardener, naturalised Briton and homosexual. Initiated as a small-budget educational TV programme, then produced for the BFI by one-time Trot Tariq Ali from a script by Marxist professor Terry Eagleton, it hardly sounds enticing. But thanks to genuinely engaging performances by Johnson and Chassay (as Ludwig, man and boy), as well as a witty script and economical direction, this turns treatise into treat. It's shot on the simplest of sets against black backgrounds, with all the money spent on costumes, actors and lights, and framed like dark Enlightenment paintings. If it ranges wide rather than deep - the philosophy is either dropped into conversation or presented like a blackboard primer - Jarman still manages to capture the spirit and complexity of his fascinating subject. Of the entertaining cameos, Quentin's epicene John Maynard Keynes (in a delightful series of pastel shirts) and Gough's miffed Bertrand Russell are the most telling.