For decades professional sport has nurtured a win-at-any-cost mentality and has paid a heavy toll for this philosophy.

Doping scandals, match-fixing scandals and, at a lower level, various attempts to win unfair advantage are now part of the sport’s narrative.

Lance Armstrong’s extraordinary story may be the benchmark for our collective loss of innocence and trust but if we’re to learn from it, we must understand how it was allowed to happen.

David Walsh is chief sportswriter at The Sunday Times in London. A four-time UK Sportswriter of the Year, he was named UK Journalist of the Year in 2012 for his work on the Lance Armstrong Story.

He is co-author with Pierre Ballester of L.A. Confidentiel: les secrets de Lance Armstrong [2004] and author of From Lance to Landis: Inside the American Doping Controversy at the Tour de France [2007].

His more recent book on the subject Seven Deadly Sins: My Pursuit of Lance Armstrong became an international bestseller and has been adapted for a forthcoming Hollywood movie starring Ben Foster, Chris O’Dowd and Dustin Hoffman. Walsh is married and lives with his family in Suffolk, England.