Like many British kids, I grew up hearing stories of George Mallory, a heroic figure who, in 1924, set off in hobnail boots and a tweed jacket in an attempt to be the first man to reach the highest point on Earth. He was a legendary figure, but his story was a tragic one. He was last seen 800 feet from the top of Everest, disappearing into the clouds, never to return.

“The mystery around George Mallory is whether he made it to the summit before he died. For me, his story is far more interesting than this question.”

Everest came into my life again while I was an intern working for the renowned studio boss Frank Wells, who was attempting to climb the world's seven highest mountains, including Everest. It was with Frank's encouragement that I rekindled my fascination with the mountain and the Mallory story.

It wasn't until more than a decade later that I woke up one morning to the headline that Mallory's body, frozen on the mountainside, had been found by the American climber Conrad Anker, who has had his own incredible battles with mountainside disaster. Everything on Mallory's body appeared to be intact apart from one thing—the photograph of his wife Ruth, which he said he would carry in his right pocket and place on the summit. Conrad, too, was caught up in Mallory's life these 75 years later; he wanted to go back to Everest to follow in Mallory's footsteps and try to establish what had happened to the pioneering climber. Conrad's story became a parallel journey to Mallory's, which would allow the film to draw parallels between different eras, and between the mountaineers' relationships with their wives.

I started to do background research into Mallory's life with his biographers, Peter and Leni Gillman. What fascinated me was that this was so much more than a mountain-climbing story—it was about a man obsessed with a dream, and it was also a love story. As I read the letters between George and his wife Ruth, it became clear that there was a kind of love triangle involving the two of them and Everest. When George was with Ruth, he dreamed of the mountain; when he was on the mountain, he dreamed of Ruth. But the closer he got to the mountain, the more it absorbed him. An image of Mallory filled out in London, where, in film vaults, I viewed the pristine 35mm footage shot while Mallory was on Everest and was fortunate to have access to some unique stills preserved by the Mallory family.

Inspired more than ever to make a film about Mallory, little did I realize what I was getting myself into. Making The Wildest Dream was hugely complex, bringing together a large film crew and some of the world's most experienced climbers. The next five years are a blur of raising money, with my producer Claudia Perkins, for a film that most people thought was impossible; finding a team of 50 or so people who could make it happen; learning to climb; watching several climbers perish ahead of us on the mountain; carting 4 tons of equipment to the top of Everest and back; shooting the highest ever staged full-costume drama (at 25,000 feet) while being chased by a monsoon; sharing a tent with a yak; and dancing with our Sherpa guides. My hands at one point became so frozen that I could not turn the pages of the script.

Somehow, despite all the challenges, it eventually came together. We were really lucky to be able to work with Liam Neeson, who narrates the film and also has a fascination with the Mallory story. Ralph Fiennes, Natasha Richardson (in her last film), Hugh Dancy, and Alan Rickman brought the human side of the story to life voicing the letters and diaries that are such a poignant record of the expedition. It moved to another level when Lisa Truitt and Mark Katz at National Geographic Entertainment, who were behind March of the Penguins, had the inspired idea to also format the film for IMAX. Finally, the whole project came full circle when Hollywood producer Mike Medavoy, a great friend of Frank Wells, came on board as executive producer.

The Wildest Dream has been a journey that for me stretches back to childhood. The mystery around Mallory is whether he made it to the summit before he died. For me, his story is far more interesting than this question, and we didn't set out to prove it either way. Mallory is an iconic figure, but the mystery remains unsolved, and the more you get to know Mallory, the more compelling his story becomes.

Plus: Check out more of the latest entertainment, fashion, and culture coverage on Sexy Beast—photos, videos, features, and Tweets.

Anthony Geffen is director of The Wildest Dream: Conquest of Everest which opens in cinemas and IMAX theaters in the U.S. on August 6. He spent 10 years at the BBC before founding Atlantic Productions in 1992, where he continues to direct and produce films. The Emmy and BAFTA winner's credits include the feature-length documentary Jerusalem: City of Heaven , the acclaimed documentary Hirohito: Behind the Myth , and the landmark series The Promised Land .