Behind the Scenes with Tommy Caldwell | The Devil's Climb | National Geographic UK

Tommy Caldwell and Alex Honnold are two of the greatest rock climbers of all time — and best friends. What inspired them to take their latest adventure, to cycle 2,500 miles en route to a daring climb of the Devils Thumb, a legendary 9,000-foot Alaskan peak? Tommy Caldwell gives us a behind the scenes look at their epic adventure.