In 1978, a US naval officer and his wife invented an extreme form of triathlon which is becoming increasingly popular around the world. Called Ironman, John and Judy Collins' creation consists of a 2.4 mile swim, a 112 mile cycle ride and a 26.2 mile running marathon. They talk to Ashley Byrne about how the event was first launched in Hawaii. The programme was first broadcast in 2014.

Picture: A recent edition of Ironman in Hawaii, Credit: Getty Images