Cast of Everest on shooting at the base camp of the world’s tallest mountain

Everest stars and director on shooting at the base camp of the world’s tallest mountain, facing their fears and portraying tragic, real-life events as closely as possible.

Jason Clarke as Rob Hall in Everest. Universal Pictures via AP

"As extreme as anything can be." That is how Icelandic director Baltasar Kormákur describes the making of his film Everest, a real-life adventure story with a tragic twist.

Chronicling a 1996 expedition to reach the summit of the world’s tallest mountain that goes horribly wrong, it was perhaps fitting that shooting the movie should prove so arduous. It was a project that led Kormákur and his cast – an impressive ensemble headed by Australian actor Jason Clarke and American star Josh Brolin – into treacherous territory.

“First we went to Nepal – Kathmandu is an extreme city,” says Kormákur. “Then you go out to Lukla, which is the most dangerous airport in the world. When we landed, scouting for locations, there was a helicopter that crashed next to us.”

Filming in the foothills of Everest was no better. “People were getting altitude sickness,” he says. “You can’t get equipment up there – no motorcycles, nothing. Apart from a helicopter, nothing can get there and they can’t land.”

With the cast and crew hiking to base-camp 18,000 feet above sea level, this leg of the shoot lasted for two weeks before the production relocated to the Dolomite mountains in northern Italy, where it was -30°C.

“We were evacuated from avalanche dangers every other day,” says Kormákur. “We had to hire a helicopter to bomb down avalanches to get that out of the way – so extreme would be, yes, the perfect word for this shoot.”

Even when the production moved to London’s Pinewood Studios, Kormákur didn’t want to fake the extreme conditions. A huge transparent box was created in which the temperature could be dropped and the actors were bombarded with real snow – though Brolin says the refrigerated box was no substitute for the real, authentic deal.

“It’s so much easier to do these scenes in the mountains, because it’s freezing,” he says. “There were three days where I couldn’t feel my feet. It’s a pain. But when you leave it, you go: ‘God! That lent so much to what we were doing.’”

Brolin stars as Beck Weathers, a Texas mountaineer, who was part of a party organised by climbing and expedition business Adventure Consultants and led by Rob Hall (played by Clarke, who was most recently seen as John Connor in Terminator Genisys). Hall plays an experienced Kiwi climber who helped pioneer the commercialisation of Everest ascents, but when a storm hits the mountain, the climbers find themselves fighting for their lives.

If this is a warning of the dangers involved in mountaineering, it didn’t stop the actors practising for real.

“Jason and Josh, particularly, spent a lot of time beforehand going up mountains,” says Kormákur. Brolin climbed Mt Shasta in California as well as a via ferrata – a mountain route equipped with fixed ladders, cables and bridges – in Switzerland, despite suffering from vertigo. “When you confront your fear that directly,” he says, “there’s something incredibly exhilarating about it.” Clarke, meanwhile, attempted Ben Nevis in Scotland and some peaks in New Zealand’s Tasman Glacier. He had trekked through Patagonia and Kazakhstan, but this was different. He climbed with Guy Cotter, one of the consultants on the film, and who helped Hall found Adventure Consultants, and recalls a “hairy” moment – dangling off a ledge in 60mph winds, 11,000 feet above the ground.

“It put us to the test,” says Clarke. “It was things like that that gave you an understanding of what these guys did for a ­living.”

Yet, Everest is about more than just gut-churning action sequences (thrillingly shot in IMAX 3-D, if you have the chance to see it in that format). Despite several contrasting accounts of what happened during the battle for survival – including Weathers' book Left For Dead and journalist Jon Krakauer's Into Thin Air – Kormákur wanted to carve his own path through the events.

“Most of the dialogue is based on what really went down,” he says, citing recorded radio conversations between Hall and base-camp manager Helen Wilton (Emily Watson), as the situation rapidly deteriorated.

It was Wilton who connected a stranded Hall, via satellite phone and walkie-talkie, to his pregnant wife Jan for a heart-rending conversation. “I listened to it with Jan, in New Zealand,” says Kormákur. “It was a very emotional moment to go through.”

Clarke also met Jan, and went hiking with her, even learning the songs she and Rob sang to each other. “I want to do due respect to his legacy as a father and the man, who he is – even to New Zealand.”

With the likes of Jake Gyllenhaal (as fellow climber Scott Fischer), Robin Wright (as Beck's wife Peach) and Sam Worthington (as Guy Cotter) also in the impressive cast, it suggests that Everest has dramatic and artistic aspirations far beyond those of the usual Hollywood disaster movie.

“Being in scary or extreme situations pulls out the real person,” says Kormákur. “I think that’s a very interesting way of revealing character.”

Heroism, bravery, loyalty, tragedy and survival – themes that loom almost as large as Mount Everest itself.

• Everest opens in cinemas today