The South African, the Nedbank Golf challenge victor previous year, recorded six birdies after the turn following a front nine which saw Grace mix two birdies with one bogey.
English duo Andy Sullivan and Matt Wallace carded three-under 69s to move to five under for the championship while former Ryder Cup victor Jamie Donaldson, who carded the first ace of 2018, is a further two shots back after a one-under 71 which saw the Welshman mix five birdies with four bogeys.
"I was a little bit rusty with some of the wedge shots but all in all I'm very pleased with the outcome". And did you know that this tournament is the second oldest Open championship in the world, having first been formally played in 1903?
Grace had three eagles as he bids for a ninth European Tour title and to complete the set of wins at his native South Africa's three most prestigious events.
Europe trail in EurAsia Cup
Despite his win, England's Casey said his opponents fought hard: "What great golf we played, but the Asians threw a lot at us".
"I think I pretty much got the most out of that round".
Saddier was joint overnight leader with Paisley but after a hot-streak on the greens on Friday he could not find his range in the third round, two-putting 17 holes and three-putting the other.
Branden Grace launched his bid for back-to-back European Tour victories on home soil by firing a lead-sharing 65 in the South African Open at Glendower Golf Club near Johannesburg Thursday. But in the final round I just want to make sure I don't get in my own way, just take it shot for shot and stay in the moment.
He'd made seven birdies and a bogey through 16 holes.
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He added that he never said anything derogatory about Haitians. "There is no other word you can use but "racist". White House Press Secretary Sarah Huckabee Sanders said Thursday "There has not been a deal reached yet".
"I've been in this situation a couple of times and I can't say I've dealt with it too well".
Another South African, Darren Fichardt, produced Saturday's best round, going eight under to sit sixth. "There are low scores out there, but you just have to avoid the rough".
The American, targeting a maiden European Tour success, is joined by Jacques Blaauw and Adrien Saddier on the same mark after rounds of six under and one-over par respectively.
Ernie Els, a five-time victor of the South African Open, made the cut after a 70 moved him to 3 under.
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During the briefing, Trump appeared to stress that his administration is "very strong" on the environment. McMaster, Trump's national security adviser, said in September.