D: Elizabeth Chai Vasarhelyi, Jimmy Chin / 100m

With Alex Honnold, Tommy Caldwell, Sanni McCandless, Jimmy Chin, Mikey Schaefer

Climbing, whether it involves mountains, cliff faces, escarpments, or domes, is always a risky, sometimes highly dangerous endeavour, even for the professionals. Imagine though, if you took away any ropes or pitons or other safety equipment, and you attemptd to climb, say, a sheer cliff face using only your hands and feet to get to the top, how much more risky, or highly dangerous do you think that would be? If you’re not sure, then Free Solo is the movie that will provide a definitive answer (as if anyone really needs convincing). It introduces us to Alex Honnold, a professional rock climber who has become famous for his free solo ascents of sites such as Northern Ireland’s Fair Head, Mexico’s El Sendero Luminoso, and the Yosemite Triple Crown – Mt Watkins, El Capitan and Half Dome. For most people, these sites will mean nothing at all, but they are all genuinely challenging climbs that Alex Honnold has completed on his own, and without any equipment to help him. But there has always been one ascent that Honnold has always dreamed of conquering as a free solo climber: the 2,900 ft Freerider route of El Capitan. And on 3 June 2017, he set out to make his dream come true…

There are several moments in Free Solo where the camera adopts a vertiginous angle, and we look down on Alex Honnold as he carefully navigates his way across and over rock surfaces that look almost smooth and lacking in finger and toe holds. But while Honnold effectively clings to those rock surfaces, the image – whether it’s courtesy of a drone or one of the team of climber photographers organised by co-director Jimmy Chan – nearly always keeps his position in context with the wider surroundings. And that context is scary. If you suffer from vertigo, or have even the slightest fear of heights, then this movie is not for you. What Honnold does, and the danger that he puts himself in, is nothing short of both courageous, and insane. And yet, Honnold is a genial individual, likeable and passionate about what he does, and quite open about his feelings on a range of matters from his own shortcomings to when it might be time to call it quits. And even if he also appears to be someone who enjoys behaving like an outsider (he lives in a van and feels more comfortable there than in a plush hotel room), his personality is endearing, and he comes across as the nerdy kid at school who grew up to do something incredibly cool. It’s no surprise to learn that he has few friends outside of the climbing community, and it’s equally unsurprising that those he does have are fiercely supportive of him.

As to why Honnold is able to do what he does, there’s a fascinating segment where he undergoes an fMRI, and the results reveal that his amygdala, which governs our responses to fear and anxiety, isn’t entirely active. Honnold takes it all in his stride, and moves on to the next stage of his preparations to climb El Capitan. His focus is incredible, but more incredible still is the actual climb. As a feat of physical endurance, it’s unparalleled. As the cameras follow him through each of El Capitan’s treacherous sections, there are moments where it seems impossible that Honnold will be able to continue, and the viewer is likely to find themselves holding their breath in anticipation of the worst happening. This sense of dreadful anticipation is amplified by Marco Beltrami’s urgent score, and Bob Eisenhardt’s precision-tooled editing. And yet, Honnold makes it look easy, smiling at times with the enjoyment of it all, and rarely looking perturbed. The movie also takes time to explore Honnold’s relationship with his girlfriend, Sanni McCandless, and how both deal with the potential for harm in what Honnold does. Inevitably, when he sprains his ankle during his preparations, they react in different ways, he by carrying on regardless, she more quietly and with forbearance. It’s unexpectedly bittersweet moments such as these that help to make the non-climbing sequences as involving as the various ascents we witness.

Rating: 9/10 – with its breathtaking, awe-inspiring visuals and jaw-dropping imagery – there are several moments where it just seems impossible that Honnold has found a toehold or a rock to grip onto – Free Solo is the kind of documentary that impresses and impresses and impresses, and then impresses some more; a perfect blend of biography matched to a tribute to human endeavour, this is best watched on the biggest screen possible so that the impact of Honnold’s achievements can be appreciated all the more.