Graeme Storm extended his bogey-free run to 44 holes but Rory McIlroy cut his lead to two shots early in the final round of the BMW SA Open hosted by City of Ekurhuleni.
Storm came into Sunday with a three-shot advantage but World Number Two McIlroy instantly set about cutting into that, making a birdie-birdie start to get within one of the leader.
The Englishman has been unflappable all week, however, and he responded with a birdie of his own on the third to get to 18 under at Glendower Golf Club.
Fellow Englishman Jordan L Smith was then at 15 under, with a group of five players five shots off the lead.
McIlroy had looked to be in some discomfort with his back problem on the range but he did not show it on the first tee as he took out the driver and, while he found the rough, he put his approach to five feet and opened with a birdie.
Storm holed a nervy seven-footer for par but Smith three-putted for bogey to drop five back.
McIlroy had spoken about the importance of a fast start and he got one, rolling his eagle effort on the par five second right up to the side of the cup for a tap-in birdie but Smith went one better, making his eagle from 15 feet to get to 14 under.
Storm needed three putts to make his par and his lead was swiftly cut to one shot.
Smith continued his excellent recovery with a beautiful tee-shot to birdie the par three third and Storm followed him in to edge back two ahead.
South Africans Dean Burmester, Trevor Fisher Jnr, Jbe Kruger and Jaco Van Zyl were at 13 under alongside Italian Edoardo Molinari, a shot clear of home favourite Thomas Aiken and American Peter Uihlein.
