John McAvoy, 35, used a prison sentence to turn his life around and become a bike-bound athlete

The first time I properly pedalled a full revolution on an adult bike I was 30 years of age. After being released from prison I bought a bike off eBay, that was actually too big for me, and started riding around my local roads. I’d trained myself to get fit during the 10 years I served for armed robbery. The death of my best friend made me want to turn my back on crime so I started doing circuits in my cell – thousands of press-ups and step-ups - then got on the rowing machine in the gym. I broke the world indoor rowing record – by 13 miles - before I left jail and set my heart on becoming a professional athlete.

After seeing a documentary on Ironman events I realised maybe I could. I taught myself to swim via YouTube videos, I bought the bike and learned road handling pretty much on the triathlon course. When you’ve spent months in solitary confinement you find it easy to train alone – I have a high boredom threshold! At first racing was a disaster. I couldn’t stop being sick and I couldn’t take in any nutrition when on the bike, so I was basically doing it starved. Now I’m among the fastest Ironman competitors in Europe, cycling 112-mile rides before completing marathon runs. On the road I’m quite a cautious cyclist, though my speed means I probably manage to avoid trouble. I ride a Wattbike over the winter and for the events I’m training for now – Ironman Hamburg and the Palace 2 Palace ride [from Buckingham Palace to Windsor Castle] - I’m cycling 400-700km a week. My Ironman success has earned me sponsorship and now I ride every day. My favourite route is a loop that takes me out from central London to Windsor Castle, it’s pretty flat and I know every pothole along the way, plus the eBay bike has long been replaced by one that’s on a par with a Formula One car!

My success has earned me sponsorship and now I ride every day