Philippe Petit’s 1974 high-wire walk between the Twin Towers of the World Trade Centre was the result of six years’ planning and an intense soap opera of behind-the-scenes collaborative tensions. Through Petit’s story, James Marsh’s film celebrates the improbable things that can be achieved by a group of truly determined zealots, and the deep cultural mark that an iconic art statement can effect. What’s most disarming, in truth, isn‘t Petit’s act itself (which is almost too daring to process), but the pure wonder that stirs around it. Petit’s reckless disregard for safety and legality in the pursuit of mythic grandeur brings out the awed child in everyone – most noticeably in the policeman captured on archive news footage just after the performance, who affects officious disapproval whilst clearly starstruck and thrilled by what he’s seen. Petit and his small gang of collaborators, meanwhile, share a strain of rapid-fire articulacy and eccentric charisma that’s hugely entertaining in itself: it’s as if Sartre, de Beauvoir and their hangers-on had taken an experimental detour into funambulism.

Somewhere behind all of this lies a lament for an earlier incarnation of New York City – in bitter financial strife at the time, but rawer and more rebellious pre-Giuliani, and confident of its unassailability pre-9/11. Marsh doesn’t push this point, however: the ultimate fate of the Twin Towers is never mentioned. Petit, when it happened, expressed his grief in The Villager: “It is a very difficult thing to talk about. Because I studied the towers for six and a half years before my walk. So I saw them as they grew like children, and when they grew up, I married them with a cable.” Petit is a romantic, a showman, and a compelling emblem for the extremes of human ambition. Using slick reconstructions as well as archive material and interviews, and backed by Michael Nyman’s music, Marsh’s deeply involving film makes an epic figure of him.