I was always brought up to have a cup of tea at halfway up a rock face.

Our fate is determined by how far we are prepared to push ourselves to stay alive - the decisions we make to survive. We must do whatever it takes to endure and make it through alive.

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.

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

Survival can be summed up in three words - never give up. That's the heart of it really. Just keep trying.

And if you give your heart to a goal, it will repay you. It's the law of the universe.

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