The Armstrong Lie, Venice Film Festival 2013, review Dir: Alex Gibney; Starring: Lance Armstrong. 122 min. Few things take the wind out of a documentary more efficiently than a subject outmanoeuvring their director. Alex Gibney, the Oscar-winning documentarian, insists that his new film The Armstrong Lie started life as a neutral profile of the disgraced Tour de France champion that was shot during his much-publicised 2009 comeback, until his admission of doping, in a prime-time Oprah Winfrey interview, dramatically changed the agenda. I'm not so sure, though: Gibney has a truffle hog's snout for trouble, and I wonder if he sensed the Armstrong machine was about to collapse and wanted to be there when the first cogs shook loose. Either way, that collapse is what he has captured. The centrepiece of his film is a double-interview: one half was shot in 2009 before the Tour, with Armstrong dramatically lit and poised in front of a black backdrop, champing at the bit to prove his critics wrong, and the other earlier this year, in a sunlit library, with Armstrong in humbler spirits and wearing remorseful-looking knitwear. The problem is that Armstrong's reputation as a consummate liar has rendered him all but uninterviewable: when he looks down the barrel of the camera and tells you unblinkingly that he never took drugs in 2009, it rather undermines everything he has to say about regret and contrition and lessons learned in 2013. Where Gibney's film succeeds is in the way it lays bare the theatre of the Tour de France to mug bystanders like me who assumed it was a straightforward cycling competition. He discloses the complex and conniving ways in which the teams operate, with domestique racers who act as glorified windbreaks for star pedallers like Armstrong, and the sudden speed boosts and fallbacks that are carefully choreographed from the team car, but are discussed by commentators as if they are naturally occurring phenomena. The film leaves you enlightened and disillusioned, but still furious at Armstrong, who seems to have drawn the conclusion that he is now a tragic hero. "I know what it took to win those tours," he maintains. It was just a little more detailed than you guys were told. Exasperating stuff, but if Gibney couldn't crack him, you wonder if anyone could.