The Combin de Valsorey is a rocky Alpine peak that stands nearly 4,200 metres above sea level near the Swiss-Italian border. Its north-west face rises 670 metres, at a gradient of about 50 degrees, steep enough that you can stand on the slope and touch the higher ground beside you without bending down.

In May 2016, when Jérémie Heitz climbed the Combin for the first time, the north-west face of the mountain looked like a vertical curtain of white, fringed by bands of dark rock. In several places, smears of greyish ice darkened the snow cover. Heitz’s ascent was nothing extraordinary in mountaineering terms: this face was first ascended in 1958, by Egbert Eigher and Erich Vanis. But Heitz was not climbing the Combin because he cared about going up – his plan was to ski down it.

Heitz, who was 26 at the time, is a professional freerider, a skier who spends his time on wild mountain slopes far from groomed pistes and resort boundaries. His speciality lies at the extreme end of freeriding: steep skiing, descending ground with a gradient twice that of some “expert” terrain in ski resorts. This activity combines two of the world’s most perilous sports – alpine mountaineering and backcountry skiing – and regularly kills a handful of its practitioners every year. Heitz had come to the Combin as part of a film project he had devised, called La Liste, which involved descending some of the steepest and tallest faces in the western Alps.

Heitz would not be the first person to ski the north-west face of the Combin; that accomplishment was secured in 1981. But the pioneers of steep skiing, who developed the sport in the 1960s and 70s, had relied on so-called pedal-hop turns, making one staccato leap after another to deal with the impossibly precipitous slopes. Heitz had a different vision.

In its early days, steep skiing’s drama had come from the fact that these slopes could be skied at all. Now Heitz sought to bring speed – up to 75mph (120km/h) – and style to a sport that once impressed through sheer audacity. The result was something remarkable – and even riskier than before. “That style of skiing is incredibly dangerous,” says Dave Searle, a British mountain guide based in Chamonix. “You can keep pushing the limits of it until you either stop pushing the limits, or you die. That’s the two things really.”

At the top of the Combin, Heitz stood on a crest of snow that curved like a frozen wave. He looked down at the clouds in the valleys far below. “You ready?” someone said on the radio. A countdown cued the camera crew hovering nearby in a helicopter: “5,4,3,2,1. Go.”

Heitz slid sideways down the first few metres, made a turn, and then cut down on to the highest grey smear of ice. Skiing on ice is not generally recommended: all skiers control their speed by making turns. That’s how they tame gravity. But on ice, the edges of the ski can’t bite, which means you can’t turn, which means you can’t slow down. Instead, you become a vector, pure speed with no directional control.

Heitz believed he could handle the ice, and he thought it would make good footage. He was wrong about at least one of those things. On the ice he lost control and started sliding. One ski came off and he began to tumble. “No, no, no,” he shouted.

Freeriders talk about the “no-fall zone” – territory so steep that it can prove lethal if you lose your balance. The no-fall zone is generally Heitz’s natural habitat, but on the Combin it seemed for a moment that it might get the better of him. Heitz himself thought he was going to fall to the bottom, 600 metres below.

He was lucky. The Combin, unlike some of his other proving grounds, is concave, with the steepest section at the top. There was no cliff below him, and he was able to manage some semblance of control with the ski he didn’t lose. He halted himself after falling perhaps 150 metres (he says the exact distance is hard to judge). The loose ski slid further below him before it, too, came to a stop.

“You OK, Jérémie?” the radio burbled. Heitz drew an ice axe from his pack and hacked at the frozen face of the slope to secure himself. He went down gingerly to retrieve the lost ski. “I really frightened myself,” he radioed back. “Let’s call it a day.”

Heitz grew up in the same region of western Switzerland as one of the pioneers of extreme skiing, Sylvain Saudan, who made his name in the 1960s and 70s with regular descents of mountain faces that were thought to be unskiable. Heitz’s idea for La Liste had been to redo his predecessor’s path-breaking descents, albeit with a twist. He compiled a list of Swiss and French mountains with enormously steep faces – hence the title – and decided to ski them in grand style, at high speed.

La Liste officially premiered in Lucerne, on the biggest screen in Switzerland, in November 2016, six months after Heitz’s fall. By ski-movie standards it was an instant sensation, and not only because it racked up hundreds of thousands of views online and made a persuasive case that Heitz was now the best freeride skier in the world. The stomach-dropping descents recorded in the film suggested that Heitz had achieved something truly new in the sport. His fusion of style, speed and extreme danger produced scenes that are almost literally breathtaking. Much like Alex Honnold’s ropeless ascent of the vertical rock formation El Capitan in Free Solo, Heitz’s daredevil plunges, at once terrifying and beautiful, offer their audience an experience of pure astonishment. To see him in full flight was to wonder whether you were watching a man or a comet.

Like big-wave surfing, extreme skiing has always carried an existential charge: its dangers are not incidental or extraneous, and death is not a rare accident that only occurs when things go terribly wrong. Doug Coombs, an American whose style was once compared to “a droplet of water trickling down a rough plaster wall”, plunged to his death in the French resort of La Grave in 2006. Shane McConkey, a Canadian who was pivotal to the development of wider skis in the 1990s, lost his life in 2009 in an attempt to combine skiing with Base jumping in Italy. Swedish pro skier Matilda Rapaport died in Chile in 2016 while filming for an extreme sports video game, the title of which was, simply, Steep.

It was for the sake of one of his viewers – his mother – that Heitz had been initially reluctant to include footage of his fall on the Combin. He was not eager to show her how close he had come to dying that day. But one of the editors of La Liste, a Swiss film-maker called Nico Falquet, who had known Heitz since he was a child, insisted that the fall belonged in the film. It was, he said, the most dramatic moment.

Heitz eventually relented, and today he says that showing his fallibility on screen was central to the film. This, Heitz told me recently, is the simple reality of this kind of skiing. “There are times when things go well, and times when things go badly,” he said. Transparency was not the only virtue of the footage: to see Heitz stumble and fall, in the middle of a film full of inhumanly beautiful performances, was to be reminded just how dangerous what he was doing truly was. As American climber and Free Solo film-maker Jimmy Chin puts it in one of Heitz’s films: “Serious ski mountaineering, you are free soloing. You can’t make mistakes. You blow an edge. You fall. You die.”

Before La Liste, Heitz had been a well-regarded, if largely unknown, professional freerider. After La Liste, his name was spoken with awestruck admiration. “I think Jérémie is probably one of the greatest living freeskiers or freeriders or even skiers, if you want to take away the qualifier of what type of skiing,” says Drew Tabke, an American skier who competed with him. “You see a picture of him making turns down one of those faces, and there’s just something universal.”

The success of La Liste offered Heitz and his skiing partner on the project, Sam Anthamatten, immediate material rewards. Today, Anthamatten is supported by the US brand North Face, while Heitz has become a favourite for European outdoor brands. Scott, the Swiss firm that manufactures his skis, sells a model “made by and for Jérémie Heitz”, which it describes as “a true freeride weapon”. Mammut, a Swiss apparel firm once known for high-quality but rather staid mountaineering and ski touring kit, marketed a La Liste jacket in pursuit of a younger customer base. Reusch, the Italian glovemaker, has a Jérémie Heitz glove.

Today, Heitz makes about 300,000 Swiss francs (£273,000) a year; many pro skiers would count themselves lucky to make a fraction of that. The sponsorship money has allowed him to focus entirely on his film projects. He generally skis for eight months of the year, from the autumn, when the snow first accumulates in the northern hemisphere, through to July, the end of the season for high-altitude faces in the Alps. While both Heitz and the sport of steep skiing are closely rooted in the European Alps, Heitz’s pursuit of increasingly impressive lines has taken him to Canada, the US, Pakistan, Peru, Spain, Japan, Chile, Russia, Turkey and Argentina.

Heitz’s most significant sponsor is Red Bull, the Austrian drinks brand. When Heitz signed with the company while he was making La Liste, he knew he’d ascended to a new plane. In the years since, their collaboration has allowed him, as he likes to put it, “to play the game” at ever more rarefied levels. For Heitz, jouer le jeu means operating in the strange world where commercial imperative and athletic ambition meet. That can potentially also create a whirlpool effect, dragging athletes towards ever more ambitious, and more dangerous, objectives.

I got a chance to ski with Heitz last April, at Les Marécottes, the tiny Swiss resort where he learned to ski. He picked me up at the train station in Salvan, a village in the Vallée du Trient where he grew up, and drove me to the chalet he built in 2017-18, which sits at 1,100 metres altitude on the edge of a village called Les Granges.

By Swiss standards, Heitz grew up in modest surroundings. “When you think of Switzerland, you think of big chalets and you think of all the skiers that grew up going to private schools,” says Jancsi Hadik, a ski photographer who first visited the Heitz household in the mid-1990s. That wasn’t Heitz’s background. “When I visited them it was a two-bedroom little place on top of a coffee shop in the main street of Salvan,” recalled Hadik.

Heitz himself says that he would have never guessed that someday the money he earned from skiing would make it possible for him to build his own house. Built largely from larch, his chalet looks out over the Rhône valley to the alpine peaks beyond. Downstairs, the whole of the ground floor is an open garage space, effectively an enormous gear closet that, on the day I visited, was awash with skis.

The house gives an impression of stability and calm that reflects Heitz’s quiet, modest personal bearing. But his girlfriend, Louise Janssens, with whom he lives, acknowledged that the apparent placidity rests on hazardous foundations. “Sometimes, I worry,” she told me. “I have a friend who lost her boyfriend, a young guide on the Matterhorn. And when I see her I can only put myself in her place, because the same thing could clearly happen to Jérémie. I can’t imagine that tomorrow he won’t be there. So I really try to stay positive and tell myself that thanks to his way of skiing, thanks to his skill, he will also be able to manage the risks.”

The morning I arrived, after a brief stop at the chalet, we set out to ski. We ascended to the top of the Les Marécottes lift system, bootpacked up a slope beyond the chairlifts to a col, the lowest point of a ridge connecting two mountain peaks, briefly cruised downhill, then climbed several hundred metres up a shoulder to the left. On the ridge at about 2,600 metres, the sun was out and the snow around us was light and powdery.

The upper section of the shoulder was steep, maybe 45 degrees, and where two other skiers had just made a dozen turns on their way down, when Heitz descended, he jumped over a rock, made maybe two turns and was immediately at the bottom. I’d spent a lot of time that winter with skilled practitioners, instructors and guides. Heitz was an order of magnitude better than any of them – better than any skier I have ever seen. Like most of the best freeride skiers, Heitz is small – about 170cm and 66kg – his low centre of gravity helping maintain balance on the unpredictable terrain.

Heitz was on skis before he was three years old. By the time he was seven he was training for races with the local club. He never won any big competitions, but he was so proficient that coaches kept him on the team. Slalom, which requires swift, short radius turns, was his best event, and his least favourite. “I was small and technically good,” he told me. “But on the other hand, I love downhill and super-G, things that go fast.”

Heitz says the regular experience of losing was crucial to his later development, giving him a determination to continue even when things were not going well. But he could also be temperamental. If something didn’t go right in a race, he would sometimes disappear into the forest for hours to calm down. In 2005, when he was turning 16, Heitz gave up racing: not only was he clearly not going to make a career in the traditional disciplines, but he also chafed against the rigidity and regimentation of conventional ski competitions.

The following winter, he fell into the orbit of Nico Falquet and his brother Loris, two local film-makers who were working on an experimental film project about night-time skiing. At the time, Heitz was working as an apprentice landscape gardener, and at the end of his work days he would head up to Les Marécottes, where he would ski and film with the Falquet brothers into the small hours. Through the Falquets, people started to notice Heitz. “This kid skis better than you,” Hadik recalls telling the brothers, after he watched Heitz ski with them. Dédé Anzévui, a Swiss mountain guide who made the first ski descent of the Matterhorn in 1989, has recalled hearing about “this kid in Les Marécottes who’s an extraterrestrial”.

It was the Falquets who first taught Heitz that there might be money in skiing. The film they were shooting in the winter of 2006-7 was partially sponsored by the surfing company O’Neill, which was then trying to get into mountain sports. When shooting, Loris lent Heitz his O’Neill jacket. It was wildly oversized – Loris wore an XL – but it suggested to Heitz the possibility of a paying future for him, a way to live a skiing life that didn’t involve being a part-time gardener or an instructor. “It was too cool. I talked about it everywhere,” Heitz recalled. “I was super-proud to be playing the game.”

While skiing is classically an individual sport, skiing alone on wild terrain is deeply ill-advised, and partnerships are key to freeriders’ careers. Likewise, steep skiing blurs the lines with mountaineering, since getting to the top of the best slopes often involves a difficult ascent. And as soon as ropes are involved, you also need someone to be on the other end. Since 2010, Heitz has worked with Anthamatten, who is a specialist in rock and ice climbing, as well as skiing. Their partnership fused Heitz’s racing DNA and Anthamatten’s high-mountain skills, a combination that would prove central to La Liste.

Although there are freeride skiing competitions – such as the Freeride World Tour, founded in 2008 – it has become clear over the past decade that athletes do not necessarily need these competitions to maintain public visibility. Freeriders happily admit that their sport largely exists to be seen on a screen, and the goal even on the mountain is to look good. “The finished product is a three-minute highlight reel,” Tabke, the American freerider, told me. Social media meant that they could become their own brands. “It’s complicated, but I think today it’s more important to have 50,000 followers than to win a stage of the Freeride World Tour, for the brands,” says Léo Slemett, the French freerider who won the tour in 2017.

These days Heitz has more than 91,000 followers on Instagram. On his profile page, a picture shows him wearing a Red Bull beanie, and the logos of his major sponsors all feature prominently. In the wake of La Liste’s success, Heitz reached the top tier of extreme sport. “We need brands to live our passion, and brands need us,” Slemett told me. “It’s a tacit, unspoken agreement that has always worked like this, but it’s poorly paid compared to the real risk.” (In 2016, Slemett’s girlfriend, the snowboarder Estelle Balet, herself a winner of the FWT in the snowboard category, was killed in an avalanche in Switzerland.)

Heitz, for his part, was willing to play the sponsorship game. During my visit last April, when I suggested that Anthamatten could afford not to work as a mountain guide “à cause de” – due to – his sponsors, Heitz corrected me politely yet firmly. À cause de is pejorative, he said. Better to say, “grace à”: thanks to.

I sensed part of Heitz’s drive came from his own personal background. His father had left when he was a small child (though his stepfather, a mountain guide, later became an important mentor). By Swiss standards, his family weren’t rich, and he was physically always a slight kid. Playing the game was a way out, and maybe a way to prove something, too.

For all the freedom that Heitz’s sponsorships have provided him, it also seemed clear to me that this freedom comes with its own kinds of constraints. Though the brands themselves say they never demand that their athletes take on certain objectives, in reality it’s a more delicate dance. As Nico Falquet says, many skiers feel that if you don’t deliver material that is both dramatic and beautiful your contract is likely not to be renewed. “It’s business. I mean, if you can no longer deliver your rolls to all the cafeterias in the region, they will look for another baker.”

To spend much time in Heitz’s world is to encounter something like the normalisation, even the banalisation, of premature death. “To be honest, there are so many deaths that it’s not like it’s the elephant in the room, because it’s not a secret how dangerous backcountry skiing is,” Tabke told me. I was speaking to him shortly after the death of Tof Henry, a French freerider whose style was sometimes compared to Heitz’s. “Tof, who just died, is one of, like, 20 of our friends who have died. I know dozens of people who have died, and there’s not that many practitioners.”

Something that comes up often in conversations with steep skiers is the notion of managed risk. Heitz’s admirers like to emphasise his control, his coolness, the careful way he makes decisions. “I worry less about Sam and Jérémie than I do about other people,” Tabke says. “If anybody can do it safely it’s that partnership, just their skills and knowledge and approach.”

The notion that skill and meticulous preparation can mitigate danger is an appealing one – but it is a partial truth at best. Mountains are unpredictable environments, and the management of avalanche risk in particular remains an inexact science. There’s a haunting scene in the Falquet brothers’ 2012 film A Secret Spot, in which four skiers, including Heitz and Anthamatten, ski a huge face on a peak called Le Génépi near Heitz’s home in the Vallée du Trient. At one point, Loris dislodges a cornice, which triggers an avalanche so large that it almost takes out their parked helicopter below. Afterwards, having narrowly avoided writing off an extremely expensive aircraft, everyone looks rather sheepish.

When I spoke with him, Heitz admitted that the idea that you can manage all the factors is a fantasy. “Often, on the majority of faces, if you fall, you’re going to the bottom,” he told me at his chalet.

“And you’re OK with that?” I asked him.

“Well, yes, otherwise you wouldn’t do it. But it also something that’s fading as I get older, and I don’t know now I will approach things in the same way.”

“Have you lost any friends?” I asked.

“Of course. And then having accidents, like losing a ski on the Grand Combin, these are all things that will never be erased from my head. It stays there. You’re setting yourself up for something if you don’t think about it, but it’s there.”

Heitz told me that since the winter of 2006-7, when he watched his stepfather ski down the north face of the Tour Noir, a peak on the Swiss-French border, during one of his first sorties with the Falquet brothers, he’d been more concerned for the safety of those around him than for himself. Yet when it came time to film the follow-up to La Liste, in 2018, he would be confronted with a situation that brought to the fore all the tensions involved in using hazardous mountain sports to sell Gore-Tex and energy drinks.

After La Liste, Heitz and Anthamatten wanted to take their style of steep skiing beyond the Alps. “Sylvain told me, ‘Jérémie, the Alps are over now. You have to be somewhere else, in the Himalayas,’” Heitz said. “For skiing, and for me, that is the future.”

La Liste was made on a budget of 130,000 francs, most of which was swiftly absorbed by the cost of the helicopters needed for aerial photography. The money was enough for 15 days of shooting big descents, with other, cheaper shoots for interviews and what the director calls “lifestyle shots” – Heitz at home, etc. The success of the film meant that a sequel could be produced on another scale entirely. This time Heitz and Anthamattan were able to secure about 2m francs (£1.85m) for a film, the majority of which came from Red Bull. That was enough to take a film-making crew to the Andes and to the Karakoram in Pakistan. Going to South America and Asia would be a completely different undertaking than their previous projects in the Alps. In the Karakoram mountain range, even just reaching their remote base camps could require as many as 60 porters to carry their supplies.

Their first target was a 6,025-metre blade of ice and rock in Peru called Artesonraju. In 2018, Heitz, Anthamatten and the other three members of their crew set off for the summit from a camp on the glacier below. It took 12 hours to reach the peak, with the final stretch on a narrow ridge. On the way up the snow conditions seemed good, but the winds they met during the climb had transformed the south-east face into a mix of crust and hard ice.

Mika Merikanto, a Finnish photographer and experienced steep skier, went first. He skied down the first third of the face, then radioed to say the conditions meant high-speed sweeping turns were not possible. Anthamatten and Heitz followed, taking on board the advice and eschewing their usual grand style. The two athletes paused briefly where Merikanto was standing, then continued on their way down. In the interim, waiting, Merikanto had become very cold. He set off again, but lower down the face his ski hit a concealed rock and he lost his footing. His skis came off, and soon he was cartwheeling down the mountain. Watching after his own descent, Anthamatten thought Merikanto was dead. But Heitz, about 150 metres away, traversed furiously and was able to reach Merikanto’s sliding body in time to stop him, using his own body as a barricade. “It was so steep I couldn’t move,” Heitz recalls. It took an hour before anyone else in their crew was able to reach them.

The team were eventually able to contact the Peruvian authorities on a satellite phone, but they said it would take 24 hours for a helicopter to reach them. It was clear that Merikanto would not make it that long. He had sustained a spinal injury, a punctured lung, damage to both knees and an elbow, and had a bleed on the brain. He was drifting in and out of consciousness, and was rapidly becoming hypothermic.

The crew decided to bring Merikanto down the mountain themselves. They improvised a sledge from skis and managed to get him down to their base camp, where they bundled him into a tent with flasks of hot water in his sleeping bag. A few hours later, Peruvian porters arrived and helped them bring Merikanto down to a lake, which they crossed in a small boat. Finally, 15 hours after Merikanto’s fall, they reached an ambulance waiting for them.

Merikanto recalls that Heitz was next to him when he woke up in a rural Peruvian hospital. Heitz told him he was done with skiing. “He was blaming himself a lot for it,” Merikanto told me. “Blaming himself so much for it. And I guess I was just trying to calm him down a bit.”

Heitz does not dispute this. “He was there for my project,” Heitz told me. “So it’s clear that if I hadn’t had this project, he wouldn’t have come and he wouldn’t have had this accident.”

After the accident, the team abandoned the Peruvian expedition. Heitz’s girlfriend found him in a similar state of mind when he got back to Europe. “He came back from Peru and told me he was stopping skiing,” Janssens recalled. “He told me, ‘I don’t want it any more, I’m selling my skis, I don’t want to hear about skiing any more.’”

In Switzerland, Merikanto began a gruelling process of rehabilitation. Eventually he would walk again, and even ski a little, but he can no longer move as he once did.

After Merikanto’s near-fatal accident, a question mark loomed over the film. Heitz says there was no pressure from the sponsors to continue, and after deliberating, he and Anthamatten resolved to finish what they had started.

As they prepared for their second trip, to Pakistan, Anthamatten and his girlfriend split up. She had long been uncomfortable with the way he lived his life, but Peru was the final straw. Shortly after the team arrived in Islamabad, they learned that three climbers – who, like Anthamatten, were sponsored by North Face, and whom both Heitz and Anthamatten knew personally – had died in an accident in the Canadian Rockies.

Heitz and his crew had no further accidents, but they found in Pakistan what they had already discovered in Peru: doing their style of skiing at approaching 6,000 metres, at the end of tenuous supply lines, in mountains they did not know, was barely viable. They filmed some striking descents, in particular in the Snow Lake region of Pakistan’s Karakoram. But they didn’t have the volume of footage that made the first La Liste a sensation.

“They didn’t have much luck with the skiing,” Merikanto told me. “They really didn’t have much material without the accident. And then it kind of went a bit nasty.” In Merikanto’s telling, Red Bull, the primary sponsor of the project, wanted to centre the film on his injury to make up for the absence of extreme ski footage. Merikanto didn’t want that.

A standoff ensued. Merikanto hired a lawyer, and eventually he struck a deal with Red Bull for an undisclosed sum. In return, he agreed to let the story of his injury be used in the film. La Liste 2 premiered in 2021. Subtitled Everything or Nothing, it is a very different production from its predecessor. The film is primarily the story of Merikanto’s injury and rehabilitation, along with Heitz’s growing uneasiness about the risks involved in the project. His decision to turn back on Laila Peak in Pakistan while Anthamatten continues is portrayed as a signal moment.

Red Bull turned down a request for an interview for this article, though one of Heitz’s contacts at the company, speaking on the condition that they not be named, told me that Red Bull did not suggest ideas for projects. The athletes came to them. “Having Red Bull as a partner is like insurance for an athlete,” Heitz said. “OK, it’s a drink brand, it’s not an insurance brand. They do a lot of marketing. But they are aware that they sponsor extreme-sports athletes. They started like that. They have been there to help every athlete who has had accidents. If you get injured, they have a centre in Austria. You can recover at their expense.”

Merikanto appears to hold no grudge against Heitz – they remain friends – but he finds it hard to justify the risks involved in the sport. “It’s a waste of incredible people, personalities. I feel it’s a waste,” he told me. “Somebody dies and then on the next day you have your social media, full of this ‘ride in peace’ bullshit. And then the circus continues.”

When Tof Henry died, in October last year, he was with Mathurin Vauthier, a French photographer based in Chamonix. Afterwards, Vauthier published a long post on Instagram describing what had happened to Henry and Juan Señoret, the Chilean skier who died in the same accident. It read like an anguished howl for lost friends. “They were at the peak of their joy and their reasons to live. Skis on the feet, a sublime mountain, a sunrise, and with a partner who shared the same vision.” Then, below, Vauthier added: “Finally, thank you to the sponsors, without them nothing would have been done in the same way.” I wondered if he was aware of the irony, or if the brands listed were either.

On the second day I skied with Heitz last year, we drove towards the French border up a forest road. It was a spring morning, there was no snow on the ground, and liverwort flowers poked from the turf. For the next five and a half hours, as we climbed up towards a 2,628-metre peak called Bel Oiseau and then descended again, I had a sense that Heitz was oscillating between two states of being. He had been a professional steep skier, maybe the best in the world. He had played the game as well as anyone. But now he was 33, and ageing out of peak athletic performance. He told me he had pulled back from the craziest risks after Merikanto got hurt. He was slowly leaving behind that old life, and moving towards a new one. He was training to be a European mountain guide, which involves reaching a high standard in climbing on rock and ice as well as skiing, and usually takes an investment of time comparable to a PhD.

We carried our skis, and then, once the snow had thickened, we climbed using skins – strips, once sealskin, now synthetic – attached under our skis for traction on the snow. Heitz set a ferocious place. I am pretty fit, but I still lagged behind. Every so often, he vanished out of sight. We climbed without pause for 1,300 vertical metres. We passed chalets, then the tree line. Finally, he waited for me to catch up. As we approached a ridge that ran north-south at above 2,500 metres, he showed me how to dig the heel of the downhill ski into the snow below to make a firm platform when changing direction between uphill tacks.

When we reached the ridge, the glory of ski mountaineering opened out before us: an empty crest, the quiet, the lake far below. A couloir – a steep gully – plunged down on the left-hand side of the ridge. Heitz fastened a sling around a boulder and fished a climbing harness out of his pack. “It’s a prototype,” he said, as he pressed it on me. “Not been tested yet.” It was clear he was joking, but I was still apprehensive, in part because I had no idea what the plan was.

Heitz lowered me down to the start of the couloir. I reached a position where I could stand without sliding, unroped. Heitz jumped over the crest and skied down to where I was. He put a ski pole on the slope and held an iPhone clinometer against it. “Fifty degrees,” he said. “That’s the same slope as the Lenzspitze, more or less” – one of the peaks from La Liste.

It was extremely steep, but the snow was soft, and that changed everything. The steep pitch continued for only around 80 metres before it eased, with no cliff beneath us. I side-slipped the first sections, and then Heitz showed me how to turn on slightly gentler ground. I was relieved when it was over.

For the rest of the day, Heitz remained in full-on instructional mode. He was a different person from the one he had been when we had set out: earlier he had kept a distance, now he was gracious and engaged. It was clear that he would be a good mountain guide, even if the only clients he’ll take out may be the oligarchs who have seen his films, and even if part of him would miss the danger that had defined his life ever since he was a teenager. We skied down to the woods and back into springtime.

More recently, when we spoke, Heitz seemed reconciled to his new life. He told me that he has no ambitions to take his skiing even higher, on to 8,000-metre mountains, the very highest ground on the planet. His aim was “to be as versatile as possible in the mountains”. That meant skiing, certainly, but also rock climbing, and paragliding. He wanted, he said, “to be a Swiss Army knife”.