LaShawn Merritt pulls up in 400m

Defending champion LaShawn Meritt has missed out on qualification for the semi-finals of the 400m after pulling up in his heat with an injury.

The American started slowly out of the blocks and he failed to recover before abandoning his attempt to qualify.

Merritt was reported to be suffering with an Achilles injury before the Games and the 26-year-old appeared to aggravate the problem in the first 100m.

Team GB's Conrad Williams did qualify for the semi-finals in third place, with Lalonde Gordon and Steven Soloman the only competitors ahead of him.