I arrived in my mid-fifties, clinically obese, riddled with arthritis and often having to walk with a stick.

I had an epiphany, threw away my stick and resolved to change my life for ever. I started walking every day. The walking turned to running and after two years I had lost a third of my body weight and was fitter than I had been since my twenties. I started running all over Europe and pushed myself harder and harder. In 2015 I ran eight self-supported marathons in eight countries in eight days driving myself between each one - a world's first. As I approached my sixtieth birthday, I wanted to mark it in a really spectacular way. I decided to emulate the world's greatest trail runner, Kilian Jornet, and run across Spain from the Atlantic to the Mediterranean. The journey would take me 525 miles across the Pyrenees climbing a total of more than 125,000 feet - the equivalent of four 'Everests'.

This is my story.