FEW figures in the film world are as intriguing as Roman Polanski, the indisputably great artist whose tumultuous life behind the scenes has become better known than any of his films. That he had ''unlawful sex'' with a 13-year-old girl in 1977, that he fled a prison sentence in the US to live in Europe, that he was confined under house arrest in Switzerland in 2009 while the local court considered a fresh demand from US authorities for his extradition - this has become Polanski's central melodrama.
It was during those seven months of house arrest that the Polish director's friend and producer, Andrew Braunsberg, persuaded him to film a talk on his life. Initially, it was a sort of therapy. ''He was obviously in a deep depression,'' Braunsberg recalls.
Polanski, 79, is married to French actress Emmanuelle Seigner, 46. They have two children. Braunsberg suggested shooting a memoir ''just for ourselves and for his children, to have a record of his life where he would really tell the truth on a deep level. He loved the idea.''
A small crew of longstanding intimates was assembled and Braunsberg, having decided against preparing any questions, started talking to Polanski almost at random.
They shot 15 hours in all, and somewhere in the middle, director Laurent Bouzereau was invited to look at the footage and see if a documentary could be made. Bouzereau had already filmed Polanski on set for some DVDs.
''He is extremely demanding,'' he says, ''but I have never seen a crew so dedicated to one man. And I have no doubt he could do everybody's job better than they can.''
Whether Polanski told enough of the truth, or told it in sufficient depth, is open to question. Braunsberg says he was able to ask anything, but critics have objected that the pair skate over the charge of statutory rape. This is unfair, Bouzereau believes.
''It was never the intention to be the Oprah of Roman, so of course it was hard to be objective,'' he says. Moreover, ''he admits there is no excuse for what he did - he says it was wrong.''
But that is all he says. The only light shed on Polanski's precipitate fall from grace is a vague glimmer from the facts already known - but set out here with resonant clarity - about the grisly gang murder of his second wife, Sharon Tate, in 1969 and the subsequent suspicion cast on Polanski by a gossip-hungry press. By Bouzereau's account, he lived through a nightmare that might have driven anyone mad.
However, it is the Jewish Polanski's memories of his childhood in the Warsaw ghetto that are unquestionably the most affecting part of the film, partly because they could be the memories of so many others. Several times we see his eyes fill as he recalls the overnight disappearances of his mother and sister, the kindness of people who sheltered him, his bitterness when his father married again, and his reunion with his sister. He is, apart from anything else, an extraordinary storyteller.
Polanski was not deported - as long as he stays out of countries likely to respond to the next US extradition demand, he is free. The court's decision gave the film a third act, Bouzereau says, and Polanski is back behind the camera. It is, after all, the film buffs' Polanski - creator of his first Polish feature, Knife in the Water, of the terrifying Repulsion, of Chinatown, Rosemary's Baby and The Pianist - who will be remembered. Unlike their author, the films never went wrong.
Roman Polanski: A Film Memoir opens at Cinema Nova on February 21