For the survival drama The Mountain Between Us, director Hany Abu-Assad insisted stars Kate Winslet and Idris Elba experience the harsh reality of a mountain environment.

Based on Charles Martin’s bestselling romance, The Mountain Between Us begins one stormy night as two strangers await a flight from Salt Lake City airport. Ashley Knox is a successful photographer heading east for her wedding the next day, while neurosurgeon Doctor Ben Payne is flying to Baltimore for life-saving surgeries.

After chartering a small aircraft together, their pilot suffers a heart attack and the plane crashes. The two strangers must forge a connection to survive the extreme elements of a remote, snow-covered mountain.

Playing the stranded couple, Kate Winslet and Idris Elba have enough heat to melt the snow, although they will need more than chemistry to survive. When they realise nobody is coming to rescue them, they embark on a perilous journey across the wilderness.

Winslet and Elba seem like a couple made in movie heaven, but this might have been a very different film. It was originally set to star Michael Fassbender and Margot Robbie before both had scheduling conflicts and were later replaced by Rosamund Pike and Charlie Hunnam, who likewise eventually dropped out. Perhaps they don’t like the cold?

Director Hany Abu-Assad insisted on his cast getting real, shooting the film in the snow-covered mountains of British Columbia outside Vancouver in Canada.

“We really are at 10,000 feet and we really were freezing cold and it was very difficult”

Not that Winslet complained: “I think you can tell if something is green-screened, and doing it for real had such an impact on our characters and the truth of the story. We really are at 10,000 feet and we really were freezing cold and it was very difficult,” says the actress, speaking at the Toronto International Film Festival.

“I’d never done anything like this before in terms of altitude. Running at altitude is absolute agony and makes your chest burn. It’s so horrible and it was the one thing about this film that I handled badly. I‘m a fit, strong person but I wasn’t prepared for that at all,” continues Winslet, adding that should she ever be stranded on a mountaintop, she would not chose Elba as her mate. “I’m pretty resourceful actually and I know how to build a fire – but Idris is rubbish.”

Shamed into improving his survival skills, Elba laughs, “If I could choose anyone to go down with in a plane, it would be Kate. Yes man.”

Clearly a fan of Canada, Elba even debuted his new girlfriend, former Miss Vancouver Sabrina Dhowre, on the TIFF red carpet.

“We made this film in Canada with Canadians and we did not want to go home,” says the actor, who had more reason than most to linger in Vancouver.

Spending almost every day of the 60-day shoot together, the pair learned to keep their distance while off-set. “We did have days where we would purposefully leave each other alone. It was like a relationship – you have to give each other space,” says Winslet.

The Mountain Between Us is in cinemas on October 12.