MALELANE, 14 Dec 2014 (AFP) - It was the South African's fifth European Tour title, the other four all coming in a remarkable 2012 season.
Grace had been five clear of the field at the halfway stage at Leopard Creek Golf Course after following a sparkling opening 62 with a round of 66.
However, a third round 72 put him at 16 under par with little-known Dane Lucas Bjerregaard closing to within one of the lead.
The door was open but no-one was able to step through it as Grace romped away to a 20 under total and comprehensive seven stroke margin of victory over compatriot Louis Oosthuizen.
Last year’s Challenge Tour Number One Andrew Johnston was third on 11 under, with Nedbank Challenge winner Danny Willett and Trevor Fisher Junior tied for fourth a whopping ten shots behind the winner.
Grace said it had been a "phenomenal week."
"It’s been a long year, a hard, year but now it’s a fairytale ending just before Christmas," Grace said.
"One of the main things this week has been the driving; I just put a new driver in the bag in Dubai and that’s been the key this week.”
Grace swiftly doubled his overnight advantage when Bjerregaard bogeyed the first after finding a greenside bunker, and Grace birdied the second after an excellent pitch to tap-in range to pull further clear.
A birdie from five feet at the fourth was followed by a gutsy par save from sand at the short fifth, but Bjerregaard up-and-down for birdie at the driveable sixth to close to within three.
However, the 23-year-old Dane was dealt a major setback at the short seventh when he found the water and ran up a triple bogey six, and his afternoon unravelled from that point as he took 50 shots on the back nine to tumble down the leaderboard.
Grace failed to get up-and-down at the seventh and sporadically came under pressure from Oosthuizen, Willett and Johnston.
The 26-year-old kept them at arm’s length by getting up-and-down at the driveable 11th for birdie and two-putting the long 13th and 15th for further gains.
A poor bunker shot at the 16th led to bogey, but nearest challenger Willett dropped six shots in the last three holes and Oosthuizen found water at the last to alleviate any lingering pressure.
Leadin final round scores on Sunday in the European Tour's Alfred Dunhill Championship played at the par-72 Leopard Creek Golf Course:
268 - Branden Grace (RSA) 62-66-72-68
275 - Louis Oosthuizen (RSA) 69-69-68-69
277 - Andrew Johnston (ENG) 69-67-68-73
278 - Trevor Fisher (RSA) 73-67-69-69, Danny Willett (ENG) 66-69-67-76
279 - Francesco Molinari (ITA) 68-65-70-76, David Drysdale (SCO) 71-68-71-69
280 - Thomas Pieters (BEL) 71-71-68-70, Tjaart Van der Walt (RSA) 67-67-75-71, Shaun Norris (RSA) 68-67-73-72
281 - Pedro Oriol (ESP) 70-72-74-65, Justin Harding (RSA) 71-70-70-70, Richard Sterne (RSA) 71-71-67-72
282 - Espen Kofstad (NOR) 70-72-71-69, Daniel Brooks (ENG) 70-72-71-69
283 - Morten Madsen (DEN) 70-66-72-75, Jbe Kruger (RSA) 68-69-75-71, Danie Van Tonder (RSA) 70-69-70-74, Thomas Aiken (RSA) 71-72-69-71, Louis De Jager (RSA) 69-67-76-71, Andrew Curlewis (RSA) 72-67-74-70
284 - An Byeong-Hun (KOR) 71-69-72-72, Hennie Otto (RSA) 74-67-75-68, Dylan Frittelli (RSA) 70-70-73-71, Johan Carlsson (SWE) 70-68-73-73