A back-nine eagle and birdie blitz propelled New Zealander Ryan Fox to an eight-under 64 and a one-shot lead on Thursday after the first round of the Nedbank Golf Challenge.
Fox, a son of former New Zealand rugby star Grant Fox, completed the front nine in one under after two birdies and a bogey in Sun City, 175 kilometres (110 miles) northwest of Johannesburg.
But the 35-year-old, seeking a third European circuit victory this year, went on the offensive after the turn and fired an eagle and five birdies.
"Club selection can be a challenge here given the altitude, but I fared okay," said the pacesetter at Gary Player Country Club.
Fox is one stroke ahead of 2023 Ryder Cup captain Luke Donald from England and three in front of Italian Guido Migliozzi.
Chasing a first victory in either the PGA or European tours since 2012, Donald picked up seven birdies, including five in the second nine, and did not drop a shot.
Migliozzi was the epitome of steadiness, collecting five birdies and parring the other 13 holes in a competition known as the "African major".
Defending champion Tommy Fleetwood from England is five shots off the pace after a 70 that included four birdies, but also a double bogey six at the par-four eighth.