The 26 year old, looking for a maiden Tour win, eagled the par five opener and birdied the next two as well as the sixth to reach 15 under par at East London Golf Club after six holes.
He was joined out in front by Austrian Markus Brier - who kept his European Tour card by the narrowest of margins at November's Qualifying School.
The two-time European Tour winner fired his pitch against the pin at the first before tapping in for birdie and followed that up at the next to be two under through two holes.
The leading pair were beginning to stretch the field - 19 players had been within three shots of the lead at one stage but there was now a two shot gap back to Open Championship winner Louis Oosthuizen, his compatriot Jaco Van Zyl and Spaniard Manuel Quiros.
With no signs of the strong winds that had kept scoring in check for most of the week, some very low rounds looked achievable on a picture-perfect day at East London Golf Club.
Brier then reached the par five third in two, and although he failed to sink his eagle effort he was left with a simple tap-in for birdie that gave him the lead.
Oosthuizen also reached the green in two at the third and two-putted for his first birdie of the day.
|T4||VAN ZYL, Jaco||RSA||18||-15|