I started to get so many letters from unlikely people; a single mum going, "I watch your show, I'm not into survival, but I hold down four jobs and I get it when you say it's about persistence and putting a positive attitude into things during difficult times." That for me was a great liberator to realize that the show isn't about me running around, jumping off stuff and flexing muscles, it's about inspiring people. That makes me really happy.

There's no magic to running far or climbing Everest. Endurance is mental strength. It's all about heart.

To get ready to climb Everest, I did a lot of hill running with a daypack on and a lot of underwater swimming. I would swim a couple of lengths underwater and then a couple above. It gets your body going with limited oxygen.

I exercise about 40 minutes a day, and I'll run one day and do circuit training the next day. I live in an area where there are brilliant hills and mountains, so I get a good hill run with my dog. At home, I'll do the circuit training with old weights, along with pull-ups in the trees and that sort of stuff.

In the British Special Air Service, combat fitness is all about running.

Exercise helps my back. If I don't exercise, that's when it starts to hurt. The pain is a good motivator to run and exercise.

I think it's fun running with dogs. They're always so fit and fast.