Len Mattiace took over at the top of the Alfred Dunhill Championship leaderboard after Thomas Aiken dropped four shots in three holes.
Overnight leader Aiken - looking to become the first home winner at Leopard Creek Golf Club in South Africa since Ernie Els three years ago - suffered bogeys at the ninth and tenth before a double bogey six at the 11th saw him drop to second with seven holes to play.
His playing partner Mattiace, an American who lost a play-off to Mike Weir at the 2003 Masters Tournament, was level par for his round and 17 under for the tournament at the same stage - a lead of one shot - as a thrilling climax brewed.
Also 16 under for the tournament after 12 holes was England’s David Lynn, who was two under for the day.
Swede Johan Edfors was two shots off the lead appoaching the 18th tee, while compatriot Oskar Henningsson - winner of The European Tour Qualifying School - was also 15 under after 12 holes.