Even the most fearless daredevils would take their hats off to Philippe Petit, the Frenchman who, four decades ago, walked between the Twin Towers of New York's World Trade Centre on a wire 410 metres in the air.
While onlookers at the time could only gaze up to see him passing eight times on the wire, dancing, laying down and kneeling, director Robert Zemeckis ( Forrest Gump, Cast Away) hopes to offer cinema-goers the story from Petit's perspective in his film The Walk.
To play the 24-year-old stuntman, actor Joseph Gordon-Levitt had to learn to walk the wire. Luckily he had a good teacher - Petit himself. After eight straight days with Petit, working from 9am to 5pm every day with only short breaks, Gordon-Levitt was able to walk a nine-metre wire two metres up from the ground.
The actor came to see balancing on the wire as a metaphor for Petit's life and creativity: "Before I met him, when I had just read his books and seen his interviews, I heard him say, 'I never fall,' and I thought, 'Well, that's arrogant; he could fall.'
"But then he taught me what he meant: he said, 'I jump, because it's a decision.' You never want to keep fighting the balance to the point that you lose control. Either you jump to the mat, or you kneel down. You do something, you don't just fall."
With just eight days of training, however, he wasn't able to do any of Petit's tricks. So the visual effects team nestled the wire into a green steel plank, and removed the green afterwards to make it look like the actor was standing on the wire.
The filmmakers also hired a stunt double and digitally replaced his face with Gordon-Levitt's. They scanned his face in 43 different poses to record all of the muscle movements his face is capable of.
But the most daunting task for the filmmakers was recreating the twin towers, which fell in the September 11 attacks in 2001. Using original blueprints and countless reference photos, the production team built a 12-metre-by-18-metre corner of the South Tower, where most of the action takes place. They also built part of the roof and used visual effects for the rest.
"If you build it perfect, it just looks fake," says visual effects supervisor Kevin Baillie, explaining that their design couldn't be too polished if it was to look realistic.
Baillie also spent two days in a helicopter flying over Ground Zero at exactly the position where Petit was to get the sensation of what it would be like to walk at such a height without safety gear. "I honestly don't think the visuals that we have in the film would have been as good if I hadn't been there to feel what that felt like," he says.
Petit was happy with the results: "It's my story, I know how it ends, yet I was secretly thinking, 'Well, I hope these guys make it!'" he says.
"For the first time in the history of cinema, they're going to actually be on the wire with me. This is a beautiful movie and I completely love what I saw."
Opens on Thursday