Graeme Storm turned in 33 to maintain his two-shot lead on another day of low scoring at the BMW SA Open hosted by City of Ekurhuleni.
The Englishman had equalled the course record on Friday with a blemish-free 63 and he extended his bogey-free run to 32 holes to get to 15 under at Glendower Golf Club.
That gave him a two-shot lead over home favourite Trevor Fisher Jnr and American Peter Uihlein and continued his promising start to the season after he lost his playing privileges last season by just 100 euros but was then handed a reprieve after Patrick Reed opted not to play the Final Series.
World Number Two Rory McIlroy - who nearly withdrew from the event yesterday and is having treatment on a back injury - was then at 12 under alongside English pair Laurie Canter and Jordan L Smith, South African Keith Horne, Frenchman Roman Langasque and Swede Richard S Johnson.
The par five second was gettable and McIlroy, Fisher and Uihlein all took advantage to close the gap but Storm made a birdie of his own to get to 13 under.
Fisher birdied the fifth and Uihlein the fourth to sit just a single shot off the lead and McIlroy soon joined them at 12 under in spectacular style.
The Northern Irishman was a long way back on the seventh fairway and launched an approach that pitched ten feet behind the hole and spun back down the slope for an eagle.
Storm faced his first scare of the day when he put his tee-shot on the sixth over the back of the green but he almost holed his chip and saved par while Fisher dropped a stroke ahead on the seventh.
McIlroy has been in the upper echelons of the leaderboard all week and when he got on the green on the par five eighth in two and made a two-putt birdie from 15 feet, he was on top for the first time.
David Drysdale outdid him with a stunning approach that left a tap-in eagle - his second consecutive eagle on that hole - and that moved him into the group of six players at 11 under.
Storm did not have company at the top for long, hitting an excellent approach into the seventh and making his second birdie of the day before Fisher and Canter both made their third on the eighth to move up to 12 under.
McIlroy then missed a very short putt on the ninth for a first bogey of the day and Storm's lead was back up to two shots.
The eighth was proving just as gettable as the second and while Uihlein moved to 13 under, Storm followed him in to maintain his two-shot cushion.
Fisher made it back-to-back birdies on the ninth to join Uhlein in second and playing partner Smith did the same to join the ever-expanding group at 12 under.
Horne joined the party three off the lead with his third gain of the day on the tenth but that was nothing compared to Johnson who, after turning in 32, made a hat-trick of gains from the 12th.
Langasque, who had returned to complete his final four holes in the morning after Friday's storms, had an eagle on the eighth and added birdies on the ninth and 11th to get to 12 under.
The back nine has been where the best of the scoring has been all week and Edoardo Molinari continued that trend as he turned in 30 from the tenth, picking up five birdies in a row from the 11th and another on the 17th.
Further birdies followed on the second and sixth and Molinari was threatening the course record at 11 under alongside Drysdale and Thomas Aiken.
