England's Graeme Storm carded a faultless 67 for a 17-under-par total and a three-shot lead over world No.2 Rory McIlroy following the third round of the South African Open.
Jordan Smith (68) of England and home golfer Jbe Kruger (69) are a further shot back on 13 under par for the tournament.
Storm, who has a single tour victory to his name at the French Open in 2007, sunk five birdies and has now gone 41 holes since last dropping a shot.
McIlroy, who has been suffering with back pain this week, was left frustrated by another poor finish to his round of 67. After bogeying 17 and 18 on Friday, he dropped a shot again on the last in the third round.
He turned in 33 after an eagle on the par-four seventh hole and looked to be on the charge having sunk three birdies in his next four.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Yet the 27-year-old Northern Irishman missed an excellent birdie chance on the 15th hole and then could not sink a 20-foot putt on 18. He remains upbeat about his chances though.
"I'm very pleased," McIlory told reporters. "I was in a bit of discomfort early on but the physio got me out to play. I started well and drove the ball well. I gave myself plenty of chances and took a few of them in the middle of the round like I did yesterday.
"It was a decent score, but I felt it could have been better. The finish was disappointing, not birdying 15 and then dropping a shot on the way in, but I'm still in with a shout tomorrow and that's all I can ask."
Storm only retained his European Tour membership card for 2017 after American Patrick Reed was removed from the money-list last year, having not played in the required number of five tournaments.
