Playing in the same group as Charl Schwartzel and Martin Kaymer, the 33-year-old Glaswegian was bogey-free on the demanding Gary Player Country Club course at Sun City as he carded a five-under-par 67 in the third round of the Rolex Series event.
With an eight-under-par 208 total, Jamieson sits a shot ahead of enigmatic Frenchman Victor Dubuisson (71), with German Kaymer (69) and South African Branden Grace (68) two strokes further back and a number of other potential threats to the Scot also lurking ominously behind them.
They include Italian Francesco Molinari, who catapuled himself into contention with a best-of-the-week 65 to sit five off the pace along with South African Haydn Porteous (67), while a big group on two-under includes former Masters champion Schwartzel (72), 2010 Open winner Louis Oosthuizen (70), former world No.1 Lee Westwood (74), Race to Dubai leader Tommy Fleetwood (67) and David Drysdale (69).
Two shots behind Dubuisson at the start, the smooth-swinging Jamieson played beautifully on one of the toughest courses on the European Tour schedule. He birdied the second, fourth and ninth to be out in 33 before rolling in a 25-footer at the 13th to claim the outright lead and then picked up another shot at the next following a majestic second with a fairway wood.
“It was much the same as the other two days probably tee to green,” added Jamieson, who is set to commute to European Tour events next season from a new home in Florida.
“The putter was just a little hotter and I got rid of those three-putts I had early in the round yesterday. I’m happy with that.”
Sitting 75th in the Race to Dubai, Jamieson came into this event needing a top-15 finish to get into next week’s season-ending DP World Tour Championship in Dubai. Barring a disastrous last day, it looks like being mission accomplished in that respect. But winning would land the laid-back Scot a whopping £940,000 pay-day, catapult him up the world rankings from 277th spot and put him in the frame for next year’s Ryder Cup in France.
“I actually didn’t even realise [that he was in the lead] until I saw the scoreboard at the 18th,” he said. “Obviously it [winning] would be the biggest moment of my career. I will be well aware of that tomorrow, so I’ve got to see if I can step up to the challenge.”
Having finished third behind Swede Alex Noren 12 months ago, Dubuisson will definitely be a danger, as will two-time major winner Kaymer and home favourite Grace, the man who earned a place in the record books earlier this year when he became the first man to shoot 62 in a major with a sparkling Saturday effort in the Open Championship at Royal Birkdale.
Grace looked to have played his way out of contention in this event after limping to the turn in 42 in Friday’s second round but came home in three-under to salvage a 75 and now has victory in an event dubbed “Africa’s major” in his sights as he chases Jamieson.
“This is one of those events you grow up watching as a South African and this is probably the event as a South African you want to win,” he said. “It’s ‘Africa’s major’ for a reason, and it’s one of those you’re going to have to play well to win, and hopefully I can do that tomorrow.”
On a day when Fleetwood boosted his bid to hold on-form Justin Rose at bay in race to be Europe’s No.1 this season, Drysdale jumped 17 places into a share of seventh on the back of an effort that contained four birdies.
It has left the 42-year-old in line for a second big pay-day in a Rolex Series event after finishing fourth behind Spaniard Jon Rahm in the Irish Open earlier in the year.