As part of a hard-to-imagine six-man playoff, Foster stopped 1999 British Open champion Paul Lawrie and rising star Trevor Immelman from adding to their trophy case. Also in the playoff were Dane Anders Hansen, Scotland's Doug McGuigan and Bradford Vaughan from the host country of South Africa.
All six finished regulation tied at 15-under par, though how each arrived there on Sunday was very different.
Foster, whose best finish up until Sunday was coincidently a second place in last year's Dunhill Championship, shot a final-round 4-under 68 but didn't take advantage of the easy par-5 18. A birdie at the last would have saved him from the dramatics he needed in the extra holes.
The resurgent Lawrie fired the day's best score with a 7-under-par 65, a lone bogey coming at the start of his inward nine. Birdies at the 15th, 16th and 18th got him into the six-man shootout.
Immelman, who's coming off his maiden victory at last week's South African Open, birdied the par-5 16th to get within two, then made an eagle-3 at the closing hole to throw his hat into the playoff ring. His scorecard showed six birdies, three bogeys and an eagle for a final round 5-under 67.
McGuigan looked to have the tournament in hand before a disastrous double bogey on the par-4 17th that cost him the lead. He rebounded, though, at the 18th with a birdie to get back into the playoff. He, along with Hansen, parred the first extra hole and both were eliminated for the playoff.
Hansen, winner of last year's Volvo PGA Championship, carded his second consecutive 3-under 69 and, like Immelman, made a dramatic eagle at the home hole to finish at 15-under for the tournament and in the playoff.
Vaughan, in front of his hometown fans, couldn't capitalize on the par-5 18th, thus denying him the victory in regulation. His eagle try on the second playoff hole just missed, moments before Foster's heroics.