After much hype of a showdown between Ryan Lochte and fellow USA swimmer Michael Phelps, it was Lochte who dominated the Olympic 400 metres at the Aquatics Centre.

The 27-year-old was never threatened and touched in four minutes 05.18 seconds to claim the first gold for the USA in the 2012 Games.

Brazil's Thiago Pereira was second with Japanese 17-year-old Kosuke Hagino third, just a year after taking bronze at the World Junior Championships.

Phelps, though, was third at the halfway stage before dropping out of the medals on the breaststroke leg, the Baltimore swimmer unable to claw back the deficit.