I spoke to one of the producers of Sherpa, John Smithson, who also produced Touching the Void and 127 Hours and asked him why it was important to tell the Sherpas’ story? “It was [the director] Jen’s original idea. She felt incredibly strongly that it was an untold story that needed to be told,” he said.

“The books, films and stories are all from the non-Sherpa adventurer/climber/tourist point of view. Of course we didn’t realise the story would evolve the way it did…”

The crew planned to start filming in 2014, anchoring the documentary on Phurba Tashi, a lead Sherpa guide who had climbed Everest 21 times and would be going for a 22^rd record-breaking summit. They would also focus on a female Sherpa who was planning to climb Everest for the first time. But while on a recce in 2013 they witnessed a scuffle between the climbers Ueli Steck, Simone Moro and Jonathan Griffith and a group of Sherpas.

The argument was ostensibly about rope fixing but it showed a deeper tension between Sherpas and western climbers and a changing dynamic in that relationship. Of the fight Smithson said: “We thought, what’s that saying about what’s happening on the mountain? It gave us an interesting way to tell the story…”

Douglas goes on to say the Khumbu Icefall is “uncontrollable and perilous” and that climate change is making it worse. Crucially he also says while a foreign climber would only have to climb it twice a season, a Sherpa could make up to 30 trips carrying supplies and kit to make the western climbers’ ascent run as smoothly as possible. For him the question is: “What is the moral justification for that?”

Smithson hopes the film will help people understand that tension at the heart of Everest more deeply. He says: “People can be guided to the very top now. They need to be fit but they don’t need to be a super-experienced mountaineer…we wanted people to understand the reality of what’s involved to make that happen. We hope it is eye opening on what an incredibly dangerous job it is being a Sherpa…because of all those extra journeys up through the [Khumbu] Icefall to carry all the kit that everybody needs now.”

“A Sherpa could make 30 trips on the Khumbu Icefall… to make the western climbers’ ascent run as smoothly as possible… ‘What is the moral justification for that?’”

But as more Sherpas became educated, plus active on social media and conscious of how much of the expedition pie they were getting compared to the western guides for the risks they were taking, the cracks in the relationship were beginning to appear. Then as Smithson says: “The aftermath of the tragedy blew out into the open all the emotion and anger. So you could really see that potential clashing of cultures. No one would have predicted the tragic avalanche or the outcome [of that], where Sherpas essentially shut down the mountain.”

Yet the film paints a balanced portrait of both sides. We’re reminded that Sherpas who work on Everest make 10 times the average wage in their homeland. Sherpa Phurba Tashi, who has been working with Russell Brice since 1998 says: “If it wasn’t for Russell I wouldn’t have a job. None of my Sherpa team would have jobs either.” They’d be working as farmers. We also hear from climbers who’ve sacrificed a great deal financially and personally to climb Everest, for many of them it’s their life’s work. As Brice says: “We bring people here to help them fulfil their dreams.”

Smithson says: “It’s a very complex issue as we’ve tried to show. Everest has been really good for the Sherpas, it’s helped a lot of them get education. They’ve earned more money than they could have done just in the fields and so on. It’s not a black and white issue.”

I ask Smithson what’s the next chapter for Everest and the Sherpas? “It’s going to be really interesting in 2016, especially after the earthquake this year. I just hope it’s a safe and normal season.”

A few months ago I’d asked Britain’s top mountaineer Kenton Cool the same question. He’d said: “Next year on Everest is going to be crucial. Everyone said this year would be crucial then the earthquake came along. I would hope that the Sherpas realise there is a lot of love and support for them following the earthquake from western climbers.”

“The outpouring of relief and money and donations pouring into Nepal after the earthquake really does show that people love that country and they love the people. And I hope that even the younger slightly more militant Sherpas realise that they need us as much as we need them.”

In the film Ed Douglas says: “When climbing began [in the Himalayas] the Sherpas had no conception of what mountaineering might be, yet suddenly there were on this journey. From being people who were just genetically really good at climbing at altitude to becoming international mountain guides 100 years later.”

“They might not still fully understand what it is that compels us to climb mountains but they are fantastically good at delivering the experience.”

It’s important we reflect on the physical and mental toll Everest-guiding inflicts on the Sherpa people and this film is an excellent place to start that conversation.

SHERPA is in cinemas from Friday December 18. It will broadcast globally on Discovery Channel in 2016, visit www.sherpafilm.com for more info.