Louis Oosthuizen made a stunning hole-in-one to hold a share of the lead with nine holes to play as he looked for a second consecutive title at the South African Open hosted by the City of Johannesburg.
The 2010 Open Champion was a shot behind countryman Branden Grace as he stood on the eighth tee but he produced the highlight of the week to send the huge crowds wild.
Oostuizen thought his tee shot was heading right and towards the water but it came back, took a big hop left off the fringe and rolled into the cup.
The second hole-in-one of the season helped him turn in 33 and move to 17 under alongside Grace, who hit back with a birdie on the ninth to turn in 30.
English pair Marcus Armitage and Jack Senior were at 15 under, one clear of South Africa's Martin Rohwer.
Former champion Andy Sullivan made the big early move, sandwiching a 30 foot birdie on the second with 20 foot efforts on the first and third to share the lead.
Armitage put an approach to ten feet at the second to make it a three way tie and when he got down in two from the fringe at the par five fifth, he led on his own.
Sullivan had missed good chances on the fourth and fifth in his incredible start but he was made to regret them as he double bogeyed the sixth after finding sand off the tee and a nasty lie with his third.
Grace bogeyed the second but hit back brilliantly, making a gain on the next after a wonderful approach from the rough, eagling the fourth from 25 feet and making another birdie on the fifth from slightly closer range.
The Rolex Series winner was in a tie for the lead when Armitage three putted the sixth and Rohwer was just a shot back after holing a long putt at the third and taking advantage of the fourth.
Sullivan missed the green at the seventh and three putted and, after putting himself right in contention, his chances looked to have quickly evaporated.
Grace hit the front with a 15 foot right to lefter on the seventh and an excellent up and down on the next kept his nose in front.
But Oosthuizen broke a run of seven pars with his magic moment on the eighth to leapfrog him into top spot.
Grace was not letting up, however, and he holed another 25 footer from right to left on the ninth to join his countryman at the summit.
Senior made birdies on the first, fifth, ninth and tenth in his first 11 holes.
Hennie du Plessis and Harry Hall were at 13 under, a shot ahead of Jaco Ahlers, George Coetzee, Min Woo Lee, Lorenzo Scalise and JC Ritchie.