As a professional climber, that's the question you always get: Why, why, why? It's an ineffable thing; you can't describe it.

People say, 'Are you insane?' But the most successful climbers are the most calculating, with the most refined sense of risk. They're hyper-conscious of safety. They're the least insane people I know.

You do wonder - when you are at 28,000 feet, the height that aeroplanes cruise at, when you are struggling to draw breath and every limb aches - why do I do this?

I grew up looking at National Geographic. I always wondered who was taking the photos and how.

Becoming a parent has changed the risk calculus for me. But it might be age, too, and seeing a lot of friends die in the mountains. Will I take the same risks I took in my 20s? Probably not, but I will always push myself in the mountains.

I am always concerned with finding the right spot and the right shot, so sometimes I forget to appreciate the skill of my fellow adventurers, but I am aware of how my life has been changed by my ability with a camera.