Man on Wire, 12A

Philippe Petit wire-walked into history in 1974, revealing the nerve of a bank robber and the soul of a poet

In August 1974, French tightrope walker Philippe Petit rigged a cable between the two towers of the World Trade Center and walked across it, more than 1,300ft above ground. To be precise, Petit made the crossing eight times in 45 minutes, and might have carried on (or fallen) if the New York police hadn't threatened to haul him off by helicopter.

Much of the pleasure of James Marsh's extraordinary documentary Man on Wire lies in hearing the story from Petit himself, as flamboyant a raconteur as he is an acrobat. The youthful Petit of the early Seventies, seen in photos and archive footage, is an elfin, wiry, other-worldly figure; today, he's just as elfin if rather more leathery. Petit clearly relishes his own myth, as great charlatans usually do: except that documentary evidence proves he's no charlatan, but a true marvel. We see Petit's great feats – photos of his walks at the WTC and Notre Dame cathedral, film of him on Sydney Harbour Bridge – but he makes them even more breathtaking through his very Gallic love of paradox. Telling of his first recce at the WTC, he recalls his immediate response: "Impossible. So now let's go to work."

Petit has a touch of the poet. A favourite word is "beautiful"–- as in, "If I die, what a beautiful death, to die in the exercise of your passion." There's a touch of Arsène Wenger in his gently philosophical bent: he recalls driving through Manhattan for the first time and marvelling at the horizontalité.(Surely he means verticalité.)

Petit psyched himself up for his feat – "le coup", as he calls it – by watching bank robbery movies on TV. Accordingly, British director Marsh couches his recreation of Petit's great day in the style of a Seventies Hollywood heist movie. Black and white footage re-enacts the surreptitious ascent of the towers by Petit and his crew, some of them in loud sports jackets and afros, as captions ("11pm, August 6") crank up the tension.

But the real grist of the film comes from the archive material, and the present-day interviews with Petit and conspirators. By its nature, Man on Wire gets you thinking about human limits and motivation. At one point Petit says of his wire-walking, "One half-millimetre of mistake, one quarter-second of inattention, and you lose your life" – but that precision marks not just the walk itself, but the meticulous preparation. You suspect that for Petit, the ecstasy of the stunt is not just in the death-defying 45 minutes, but in the months of studying architectural plans, building replicas of the WTC roof, posing as a journalist to quiz construction workers.

It also becomes clear that Petit's feat was also the achievement of his team, whose names have not passed into history. Man on Wire casts an overdue spotlight on the accomplices who also took extraordinary risks to make the event happen – the foremost risk being that they would end up jointly responsible for Petit's death. As we watch his old friends reminisce today, what becomes apparent is their absolute devotion to Petit at the time: his charismatic sway over them resembles a cult leader's.

Two of the team are moved to tears recalling the WTC walk. One of them is Annie Allix, Petit's former girlfriend, who remembers her awe of him; in a heartstopping archive photo, we see her transfixed with terror, or rapture, as she gazes up at her boyfriend in the sky. With poignant resignation, Allix recognises that in achieving his feat, Petit crossed over into the realm of celebrity and left his friends behind. Instead of running into her arms on returning to earth, Petit – as he recalls with self-congratulatory impishness - decamped with an admirer. Of another aide, Jean-François Heckel, Petit casually remarks that he followed unquestioningly: in this instant we sense that in every prodigy, there's also a monster. Heckel's reward for the twin towers coup was to be unceremoniously expelled from the United States, whereas Petit received a lifetime pass to the WTC observation deck.

A lot of good that was to him, you can't help thinking. Of course, that's what makes the film so resonant – all the more so because it's a matter that the film never raises explicitly. Against all odds, Petit is still with us today, whereas it's the twin towers that have plummeted. Your heart stops, early in the film, at an archive shot of a vast pit in Lower Manhattan. But it's a different Ground Zero – the building site on which the Center was about to rise. Petit was the twin towers' great celebrant, and their first conqueror, long before al-Qa'ida. And somehow, now the towers are gone, you can't help thinking of Petit as an oddly ghost-like figure himself.