Fellow American Kerron Clement retained his men's 400m hurdles crown with a world best for the year of 47.91 seconds.

BBC: Bolt storms through to 200m semis

American Kerron Clement will start favourite for the final after winning the first semi-final in 48.00, with the great Felix Sanchez also qualifying in 48.34.

BBC: Ohuruogu and Idowu reach finals

Kerron Clement of the United States took gold in the men's 400m hurdles with a time of 47.91, ahead of Puerto Rico's Javier Culson (48.09) and American Bershawn Jackson (48.23).

BBC: Idowu wins Britain's second gold