Nigel Mansell of Britain edged teammate Keke...

Nigel Mansell of Britain edged teammate Keke Rosberg of Finland to win the South African Grand Prix, giving the Williams Hondas a 1-2 sweep, at Kyalami, South Africa.

Rosberg passed France’s Alain Prost in a McLaren-TAG on the closing laps. Prost, who had clinched the drivers’ championship two weeks ago, barely crossed the finish line in third place.

Nelson Piquet of Brazil, who qualified second in a Brabham-BMW, dropped out in the early going, one of many casualties of the 82-degree temperature and the altitude of the Kyalami circuit.

For Mansell, who finished the 75-lap race on the 2 1/2-mile circuit in 1 hour 28 minutes 22.86 seconds, with an average speed of 130 m.p.h., it was his second Grand Prix win this season.

“‘Why not make it three?” said Mansell, looking two weeks ahead to the season’s final Grand Prix at Adelaide, Australia.