In 2007, the British triathlete Chrissie Wellington was the surprise winner of the World Ironman Championship in Hawaii - the first in a series of victories and world records. Wellington only became a professional athlete in her late 20s after giving up a successful career in development. She talks to Lisa Needham. The programme is a Sparklab Production.

(Photo: Chrissie Wellington in action in a triathlon in Germany in 2011. Credit: Getty Images Sport)