Christopher McDougall was a freelance writer when he came across the story of a tribe of super-athletes living in Mexico’s Copper Canyons who’d been living unchanged for 400 years. From that came Born to Run, a chaotic adventure that reads more like a Harlan Coben novel than one of the great works of sporting literature. From drug cartels, murder, an incredible cast of characters and a race through some of the most savage terrain in North America, McDougall tells Simon Clancy about how his classic came to print.