American LaShawn Merritt obliterated the field including defending champion Jeremy Wariner to win the Olympic men's 400 metres title by the widest margin since 1896.
Merritt sealed a seventh straight gold in the event for the US, starting relatively slowly before blasting down the final straight to cross the line in a personal best of 43.75 seconds.
Wariner, visibly frustrated and upset, finished a distant second in 44.74 seconds and David Neville took third with a spectacular dive for the line to complete a US sweep of the medals.
Merritt and twice world champion Wariner have dominated the 400m this year and clocked 11 of the fastest times in the world before the Olympics.
The podium sweep was some consolation for US sprinters after Jamaica took all four golds in the 100m and 200m events and both US 4x100 relay squads dropped their batons in the heats.
