You have to plan your climb before you start. All the moss and gunk, the to-do lists, the anxieties, it all vanishes

Briefly, the principle of bouldering is, there is a wall about five metres high. And you are a person, without ropes or harnesses, your only specialist equipment the shoes (which you can hire). The wall has knobbly bits poking out, colour-coded by difficulty. It is wildly exhilarating to reach the top, then – always – there’s a flash of panic when you realise, like a dog that’s run into a field of bulls, that you’re now five metres up a wall.

I started doing it a year ago because I was in love (it could have been worse; it could have been motorcross). It’s a good novice wheeze – you can get to the top on your first go – but it’s not intuitive, so I stalled at “totally rubbish, enjoying self” for a long time. There was a really experienced climber there, Louis Parkinson, who did lessons, but he was so good that it seemed disrespectful to ask, like asking Galileo to be your idiot children’s maths tutor. He’s just set up a coaching network, Catalyst Climbing, whose mission is to make it more accessible, so I sometimes have lessons now and don’t feel so bad about it.

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The first thing I learned is that every move is sacred, as it all takes energy; a move you could do at the start of a climb would be utterly beyond you after you’d been clinging on for five minutes. You have to plan it from the ground before you start, which is like turning a high-pressure hose on your brain. All the moss and gunk, the to-do lists, the anxieties, it all vanishes. The climb itself demands a kind of gymnastic strength, balance, coordination, and builds muscle in the weirdest places: your shoulders but also your thumbs; your thighs but also the backs of your calves. There’s just enough risk to make you feel heroic, and the jeopardy makes you push yourself way beyond anything you could manage with willpower.

I’m not an elegant climber, but in some moments I feel like Spider-Man. Louis, 25, looks like Spider-Man – insanely strong and long-armed, he can hang off a wall apparently for ever. He loves the movement, and the excitement, and the imagination. “It’s almost completely open to all. The two people pushing the boundaries of the sport right now are a 15-year-old American girl and a 40-something British man.” Try it, I implore you: it’s like doing a sudoku with every square inch of your mind and body.

This week I learned

Climbing gives you muscles in the weirdest places – my thumbs have never been so strong