Chinese swimmer Ye Shiwen denies doping claims
31 July 2012 Last updated at 07:36 BST
A young Chinese swimmer who won a gold medal in an outstanding performance at the Olympics has categorically rejected suggestions of doping.
Ye Shiwen - who is 16 - shaved more than a second off the world record in the women's 400 metre individual medley.
A leading American swimming coach has said her performance was "impossible".
Martin Patience reports from Beijing.