How far can the human body be pushed? David Grier has run 4,008kms across India and is the only human being to have traversed the Great Wall of China both ways, and both in world record time! David unpacks what drives the human spirit in the most challenging moments. From a ruptured kidney in India, to being arrested in Guantanamo Bay, he's seen it all. Every gruelling adventure in this legendary man's life is done with charity in mind... Miles for Smiles in particular. In his own words "It's not about me, that's why I don't give up!"