On one matter, everyone involved, on either side of the camera, in the documentary film Sherpa is agreed: it didn't turn out the way it was planned.
The film was intended to be a portrait of the people who provide the human infrastructure - who literally do the heavy lifting - that sustains expeditions to the top of Mt Everest.
Notwithstanding the now iconic images of Tenzing Norgay smiling alongside our Ed in those 1950s newsreels, Sherpas - the word is the name of an ethnic group, not a job description - sit on the sidelines of Himalayan stories.
Yet every footstep taken by a climber in that part of the world is placed in 100 footprints of the Sherpas who haul oxygen, tents, food, water and fuel to the higher camps to give climbers a chance of making it to the top.
Sherpa was intended to shine a light on the real heroes of high altitude, whom Australian filmmaker Jennifer Peedom had profiled in a 20-minute segment for a TV current affairs show in 2004.
New Zealand-born, Sydney-based producer Bridget Ikin says the plan was to focus on two Sherpas: Phurba Tashi, who was about to break the world record by summiting Everest for the 22nd time and a novice woman Sherpa on her first climb.
But real life has a way of intruding in documentaries and the intrusion on this occasion came at 6.45am on April 18, 2014. A so-called serac, a block of ice, weighing 14 million tonnes (roughly equivalent to three times the weight of all the private cars in New Zealand) crashed down on to the climbing route through the Khumbu Icefall, killing 16 Sherpas.
It was, at the time, the worst tragedy in the history of the mountain (at least 22, including 10 Sherpas, would die in avalanches triggered by the April 2015 earthquake) and it happened as Peedom and her crew were filming at Base Camp. In an instant, says Ikin, the film became not what was intended but what was happening.
There is no footage of the disaster, though the film artfully sets up a menacing expectation of it by opening with helmet-mounted GoPro footage of a small avalanche elsewhere and at another time. But the 400 hours the production did get included much of the aftermath: frantic rescue attempts; unrest among Sherpa teams about whether the climbing season should be cancelled; vocal protests against politicians who profess to care about safety; meetings between an expedition organiser, his clients and the Sherpas who made it all happen.
"We didn't know if we had a film," says Ikin. "We were just filming what was happening at the time and it was all unfolding in a very random and chaotic way and not in English." It wasn't until they returned to Australia and got the dialogue translated that the filmmakers realised what they had.
"It was nerve-racking looking for the dramatic arc that any film needs. There was a dramatic event, but did any transformation happen in it? We were lucky that Phurba Tashi made [an important decision] and we got a great interview with his wife. But we didn't know how it was going to fall and there was a lot of anxiety."
Perhaps inevitably, but to his evident chagrin, expedition organiser Russell Brice, the New Zealand-born owner of Himalayan Expeditions, becomes the film's central character. The doyen of the professional expedition community, Brice, who will be 64 in July, first came to the region in 1974 to help Hillary build a hospital.
As he was in the real-life action, he is the man at the pivot point of all the different stressors that come to bear: ensuring the safety of Sherpas; making sure the clients get what they paid for; dealing with the fallout of the loud, not to say threatening, protest action; showing respect for the cultural values of the indigenous people; dealing with politicians and bureaucrats so corrupt you couldn't make them up; and deciding whether or not to call off the season.
The film is a microcosm (albeit painted on a grand scale) of the conundrum that anyone with half a brain who has travelled in the Third World cannot avoid: is their presence destroying traditional ways of life and enabling exploitation or sustaining diversifying economies by developing businesses that employ local skills?
Speaking from his London base, Brice loses no time in telling me that he doesn't like the film. He hates the opening shot which "makes it look as though my Sherpas were in the avalanche. I've had lots of people come and ask. 'What happened to those poor Sherpas?'" And he says the film fails to adequately make the distinction between Brice's own Sherpas and the "irrational" malcontents - including Maoist hardliners - who urge Sherpas to strike for better conditions.
His particular beef is with a specific scene in which he seems to misrepresent an allegation that some Sherpas had been threatened with physical violence if they continued with expeditions after their colleagues on other teams had died.
The impression is certainly created that he was playing a double game, although it would have been to his advantage to tell the opposite story to the one he appears to tell.
Ikin ascribes the confusion to conversations taking place "without the benefit of subtitles ... In the moment, it was chaos and in that kind of environment, rumours and murmurings are rife."
And it bears adding that Brice emerges from the film as a beacon of principle, professionalism and integrity.
Brice says the agitators are losing influence because Sherpas "realise they need to get away from them because they are not taking our business in the right direction". But he laments the decline in standards among expedition companies who undercut his operation by paying Sherpas less, underinsuring them, skimping on supplies and leaving rubbish and human waste on the mountain.
"You can understand why these guys want to go on strike because they are so pissed off. But they are not educated enough to understand that each year Everest alone brings in US$3.8 million (NZ$5.6 million) in permit fees, generates $15 million internally in Nepal for hotels, helicopters and the man who sells postcards in Kathmandu. The actual expenditure is more than $110 million. A Sherpa going on strike because he feels like it doesn't understand that."
When I tell Brice that he sounds fed up, he says "Too right." "I am fed up because the authorities don't do anything. We as operators have been talking for many years long before the avalanche about how to make improvements in safety. But you don't see anything meaningful being done by these people.
"And we can't complain publicly about the local operators who are cheating, because they are the local indigenous people."
The 2016 season gets under way this month and Brice says numbers are down because of recent events, which forced the cancellation of three of the past four years. Potential clients have lost trust and are waiting to see what happens.
In one sequence in the film, a Sherpa wonders aloud whether life wouldn't be better if they returned to growing potatoes. But Brice, whose faith in the magnetic attraction of the mountain is unshaken, says "that isn't going to happen.
"In 1996 when Rob Hall died everyone said that was going to be the end of the industry, but it had the opposite effect."
What: Sherpa directed by Jennifer Peedom, produced by Bridget Ikin (pictured above) and featuring New Zealand climber Russell Brice
When: Opens at New Zealand cinemas on Thursday April 7.