Free Solo review: a sweaty-palmed account of one man's mission to do the impossible

Dirs: Elizabeth Chai Vasarhelyi, Jimmy Chin. 12A cert, 100 mins

El Capitan is a 3,000-ft-tall rock formation in Yosemite National Park, rising up from the lush valley floor like a brutalist Rushmore with the faces scrubbed out. The gruelling verticality of the peak makes it one of the world’s most popular challenges for climbers, ever since it was first ascended in 1958 by an expedition led by Warren Harding, who took 47 days to climb it using fixed ropes and pitons along the length of the route.

Even today, experts regularly die trying to master this demon, including two just this year. One Wikipedian fact to grasp is that an upsurge in recent fatalities has been blamed on increased competition, with social media fame and financial reward beckoning to whoever does it fastest and on their own.

Alex Honnold, the subject of National Geographic’s US box office smash Free Solo, has El Capitan in his sights from the start. Though this super-experienced climber has tackled hundreds of daunting rock faces unassisted – by either ropes, safety nets or other humans – he has never yet conquered El Capitan this way. No one has.

The film follows Honnold’s preparations as he squares up to the task, figuring his way around every pockmark of the peak’s “Freerider” ascent line over months of dogged trial and error. It’s the removal of the “error” component, of course, which makes the eventual attempt so petrifying: one slip and it’s over.

But watching Honnold get to grips with the climb as homework, mapping out its trickiest dilemmas, is just as enthralling. Even the names of El Capitan’s notorious set-pieces inspire a kind of awe: “Hollow Flake”, “Monster Offwidth”, “Enduro Corner”, “The Boulder Problem”. You wouldn’t want to meet any of these slippery horrors in your sleep.

Honnold’s battle plan is captured here by the husband-and-wife team Elizabeth Chai Vasarhelyi and Jimmy Chin, who previously charted their own attack on a Himalayan peak in 2015’s Meru. They have a rare degree of specialism as climber-filmmakers. Throughout, the footage they get of Honnold’s practice runs is breathtakingly close and detailed, making you wonder immediately about the logistics – and not only those, but the underlying ethics – of their own job.

There’s an axiom, credited to the French New Wave director Jacques Rivette, that every film is a documentary of its own making. Free Solo, along the way, becomes a documentary of a documentary’s making. Chin and his other crew describe serious qualms about how their shooting might affect Honnold’s state of mind.

Free soloing, by its very nature, needs absolute concentration, and the addition of extra pressure from watching eyes, or dangling cameramen, could haunt the project for the rest of time, if it translated into even a momentary loss of focus. Honnold also has a fledgling relationship to manage with a new partner, Sanni McCandless, whose emotional needs he must routinely set aside as a career climber, untethering himself not just physically but mentally to get where he wants to go.

Sanni McCandless is no relation, apparently, to Chris McCandless, the hiker from Into the Wild who fatally disappeared in the Alaskan wastes, but the name, in context, summons a certain brand of go-it-alone masculinity that would give many a girlfriend pause.

Here, too, Free Solo proves illuminating, digging down into Honnold’s family history, diagnosing his personality, to explain why his amygdala – the part of the brain’s circuitry that controls fear – seems so curiously resistant to stimulation.

When this impassive maverick has second thoughts one morning, the film crew are actually reassured – “Spock has nerves,” comments Chin, a ready source of climber-bro gallows humour (“Let’s hope it’s a low-gravity day,” he also quips). There’s a cornier obligation to watch Alex and Sanni nudged into a gradual arc of intimacy, almost as if he were a featureless slab of granite to be scaled in himself. You’d rather let the film’s impact sink in without the dead weight of Gravity, a new Tim McGraw song that makes the end credits needlessly inhospitable.

But this is nit-picking, perhaps prompted by the life-or-death perfectionism of Alex Honnold himself. The sequence of grips he must follow like a mantra to make good time – “side pull, underclang, left pocket, hand jug...” – is reeled off like hypnotic rap in a foreign language.

Sweaty-palmed as a viewer, you may envy the one asset Honnold's permitted – a bag of chalk, clipped to his waistband, which lets him balance those crucial few more pounds of himself off depressions the size of a tooth cavity. When a telephoto lens pulls back, and back, impossibly far back, he’s the one who turns into the speck. A mountain’s mass and a man’s resolve become symbiotically overpowering.