Chad Le Clos has won south Africa's second gold medal at the London Olympicsi. Photo: Reuters

South African swimming sensation Chad le Clos scooped the country's second gold medal of the London Olympic Games, edging American legend Michael Phelps in the men's 200 metres butterfly final on Tuesday evening.

Le Clos, 20, touched the wall in one minute, 52.96 seconds (1:52.96) to smash his own national record by well over a second.

Phelps, a 14-time Olympic gold medallist and the defending champion in this event, finished second in 1:53.01.

Le Clos's medal added to the gold won by Cameron van der Burgh in the men's 100m breaststroke final on Sunday. - Sapa