Usain Bolt returns to London with a shadow hanging over the 100m | Sean Ingle

Usain Bolt has recognised that athletics has been damaged by doping claims but reasserted that he is clean Usually when Usain Bolt is asked about drugs, his answers become mantras. He is more tested than other athletes. He is clean. His times can be trusted. But in the wake of last week's positive tests for Tyson Gay and Asafa Powell, Bolt appeared to understand that off-the-peg responses were not enough; a situation this worrying for the sport demanded bespoke tailoring. And Bolt attempted to p...