Climbing solo without ropes, the Canadian adventurer would scale stratospheric walls of ice that could crack and fall with one wrong move. We meet the makers of a gripping, heartbreaking new film

An insect-like creature is climbing a wall. The wall is made of ice – not regular, firm ice, but ice with spikes and cracks and gaps in behind. The creature has extended arms like a mantis, with sharply angled ends that hook into the ice, as well as spikes on its feet to kick in. Still, it doesn’t look very secure: the ice creaks and bits break off and fall. The creature feels around for somewhere else to stick its hooks and spikes, then continues upwards – intently, methodically, almost mechanically. It is both beautiful and absolutely terrifying.

When the camera pans out, it’s even more terrifying, because of the sheer size of this frozen wall. It is vast and vertiginous, the creature a tiny dot creeping upwards, a gnat in a sweeping sub-zero landscape. Except that this gnat has no wings: if it falls, it falls. Nor does it have a rope, because it’s not a gnat or even an insect, but a man – a Canadian by the name of Marc-André Leclerc, climbing solo in the Rockies with crampons and a pair of ice-axes.