Mark Wheeler battled through heat, exhaustion and two punctures to complete the toughest endurance triathlon at the National Water Sports Centre, near Nottingham.
Mark was among 1,000 other triathletes who tackled a 2.4 mile swim in the lake followed by a 112-mile bike stage through the Nottinghamshire countryside.
The Skegness Tri Club member had to fix two punctures during the bike element before returning to the water sports centre to begin a full 26.2-mile marathon.
Already very tired and with the high temperature still increasing, Mark showed great mental strength and physical fitness to continue running, cheered on by family and friends.
Mark ran the last 100m with his dad Chris by his side to finish the race in 12hr 40mins – a phenomenal achievement.