Emiliano Grillo hit the front as a first bogey for 47 holes finally cost American John Hahn his place at the top of the leaderboard in the third round of the Africa Open.
Hahn carded a brilliant 61 in Friday's second round at East London Golf Club to lie 16 under par, two shots ahead of the chasing pack, and he remained out in front thanks to birdies on the third and eighth.
However, two duffed shots on the 12th cost the 24 year old Qualifying School graduate a shot - his first bogey since the opening hole on Thursday - and meant Argentina's Grillo took over the lead on 18 under par.
Grillo, who eagled the 72nd hole to finish second in the recent Dubai Desert Classic, was putting together the best round of the day even though the previously defenceless course was finally being protected by a strengthening wind.
Birdies at the third, fourth, sixth, seventh and eighth took Grillo to the turn in 31 and he also picked up shots on the 12th and 13th to move seven under par for the day.
He led by one from Hahn with South African Thomas Aiken, Portugal's Ricardo Santos and English duo Richard Bland and Oliver Fisher two shots further back on 15 under.
Bland - seeking his first European Tour victory at the 319th attempt - had made a flying start to his round with three birdies and an eagle in the first six holes and also picked up shots on the 11th and 13th, but bogeyed the 16th after a poor drive.
Fisher looked like dropping out of contention after bogeys on the eighth and tenth, but bounced back with birdies at the next two holes.
Grillo picked up his eighth birdie of the day on the par five 15th after pitching to five feet and was soon enjoying a three shot lead as Hahn dropped another shot on the 14th.
Failing to get up and down from a greenside bunker dropped Hahn back to 16 under and into a tie for second with Bland and Aiken, the latter having two-putted the 15th for a birdie after hitting his driver off the fairway and onto the green.