Tomaž Rotar knows a thing or two about life and death in extreme environments. In February 2021, the Slovenian oral surgeon was sitting inside a cramped tent 7,300m up K2, the world’s second highest mountain. More than 20 climbers had gathered in the dark on the snowbound ledge, arriving at the camp in worsening winds and temperatures that were already below -30C.

To stand a chance of reaching the summit as the weather window they had been chasing began to close, they would have to set off again almost immediately.

Most of the climbers there that night did the sane thing; they sat tight and descended at dawn, many swallowing the fact that they had paid guiding companies at least £20,000 for a chance to reach the summit in winter, a feat that had been achieved for the first time only weeks earlier. Others felt moved to step back into the darkness and attempt what they had flown halfway around the world to do.

Rotar was among seven climbers who made the decision to go on. He only turned back hours later when he came across an unexpected crevasse. Three other climbers managed to get across it, and continued. When they failed to return, a frantic search gripped the world’s media as military helicopters and even a fighter jet scoured K2.

All three men died that night. It would be months before their frozen bodies could be found. As Rotar has followed news updates about the Titan submersible this week with a familiar feeling of dread, he has been reflecting on the calculations wealthy adventurers make when they face that vital decision: do we stay, or do we go?

“It’s the same kind of people who feel the same kind of draw, whether it’s to go deep under the sea, or to climb very high, or to run very far,” he says. “It’s a kind of sickness, like a venom in your veins that makes you want to go. Because you want that beautiful feeling that comes when the danger is over and you know you have achieved something. And then you don’t even know how you lived before that, so you go back and you do it again.”