Alex Honnold making the first free solo ascent of El Capitan's Freerider in Yosemite National Park, CA. (National Geographic/Jimmy Chin)

Con’s Score: 4 Big Boulders

Free soloing is a mental affliction that compels rock climbers to scale cliff faces without a rope. (Well, you can’t call this a sport.) No cleats, pulleys or buddy; just a cup of chalk dust and you’re ready to go. These guys put their faith in a few millimetres of rock – ancient ripples – to hold their body weight while they look for the next crack or ripple to cling to. Insane.

Alex Honnold is a well known climber who wants to scale El Capitaine in Yossemite Park which no one has attempted before. That’s because it’s some 3,000 feet of granite – or the ‘most magnificent crack on planet Earth’ he says without irony. By the end of this documentary, you’ll feel like you’ve scaled every foot.

Alex Honnold holds all of his climbing gear atop the summit of El Capitan. He just became the first person to climb El Capitan without a rope. (National Geographic/Jimmy Chin)

Alex is a likeable lad and this documentary does get under his skin and into his psyche. A father with Aspergers – and Alex being an introvert – drew him to this sport. He’s gained world wide fame and this is his Kosciusko.

It doesn’t simply recount the steps and intense preparation; it literally goes into his mind. Someone asks him to do an fMRI of his brain, and his amygdala are pretty quiet (it’s an area that processes fear, amongst other emotions). We see the impact on his relationship with Sonni, his new girlfriend, and her reactions. How do you plan a future with someone who could slip? Being in a relationship also affects his focus.

There are also lessons in how he reduces fear through preparation and knowing when to step back. Not all goes to plan and he actually backs out at one point. But these guys never give up. They just get better prepared.

Directors E Chai Vasarhelyi and Jimmy Chin have made a visceral doco. The footage of the final climb is limited, as Alex felt the pressure of cameras, but the drone footage is intense enough. I suffer vertigo and lived every step. My hands grew sweaty and I’ve never felt an audience squirm so much. His crew were just as uncomfortable. When he reached spots he’d slipped on when he was rigged up, I was in a lather.

The only reason this documentary doesn’t score the maximum is because I don’t want to encourage anyone else to attempt such madness. Intense, insightful and insane. The screen is as close as you should get to this madness.

In cinemas Jan 24

Con Nat’s – On The Screen