The last three Open Championships on the Old Course at St Andrews have produced run-away winners. At the Millennium Open, Tiger Woods won the first of his Claret Jugs by eight shots. Five years later he would win his second by a margin of five. And in 2010, at the 150th Anniversary Open Championship, the gap would be seven.

Yet it was not Woods who stood triumphant in the shadow of the edificial clubhouse. Nor was it any of 30 leading names highlighted as potential Champion Golfers of the Year before the event commenced. It was, in fact, a 27-year old South African named Louis Oosthuizen standing on the 18th green cradling the Claret Jug, having recorded as impressive and as comprehensive a victory world number one Woods had done a decade before him.

Such was Oosthuizen’s status as a 200/1 outsider, that after an opening round of seven-under-par 65, when journalists in the massive Media Centre were asked whether they would like to speak to him, only three from hundreds raised their hands. The world’s press were too busy chronicling Rory McIlroy’s stunning 63, the lowest first round, and the joint-lowest round, in Open Championship history. He had missed his birdie on the 495-yard 17th from four feet away. It could have been the best.

While the opening day had greeted players with a handshake, offering good scoring conditions, day two snarled and gnashed at the field of 156, as heavy rain and high winds battered the links.

McIlroy floundered, eventually limping home with an eight-over-par 80. But Oosthuizen strode on through the weather and signed for a 67, the joint-best round of the day. No danger now of being overlooked — the man from Mossel Bay, who hit 16 of 16 fairways on Friday, had a five-stroke lead going into the weekend. Remarkably, his leading challenger was not McDowell or Jimenez, nor Karlsson, Kaymer or Clarke. They were all in touch, but were trailing 1989 Open Champion Mark Calcavecchia, who was alone in second place on seven under.

Late in the evening on Friday, Tiger Woods had come within inches of a hole-in-one on the par-four 18th, before Tom Watson waved an emotional goodbye to Open Championships in St Andrews from the Swilcan Bridge. They were the two loudest cheers of the day and the headlines were snatched from the two-round leader. “Oosthuizen has only won once on the European Tour,” they said. “He’s missed the cut in all but one of his seven previous Major Championship appearances,” they said. “He’d slip up,” they said.

And it looked like they would be proved right as the South African three-putted the first for bogey on a third day which saw Paul Casey emerge as Challenger Elect.

Playing with compatriot Lee Westwood, Casey produced a magical performance. An outward nine of five-under-par 31 was followed by nine straight pars on the more challenging inward half, leaving the 33-year-old very much in touch at 11-under-par. To many, it seemed like his time had come.

But those who had predicted Oosthuizen to falter would be proven categorically wrong. After the first-hole stumble, the 2010 Open de Andalucía Champion did not put a foot wrong in crafting a round of 69, two-under-par, which left him four shots clear. Not once did he look burdened with pressure, or show signs of nerves. It was merely business as usual.

So it would be on Sunday, a day which Oosthuizen did not allow to become dramatic. Having opened with seven straight pars, a bogey at the 175-yard, par-three eighth brought him back to within three strokes of Casey, who had made a steady, level-par start.

But that was as tight as it would get. On the ninth, a 352-yard par four, the South African calmly withdrew his driver from the bag, opened his shoulders, and fired the ball, arrow-straight, onto the green. It came to rest 40 feet from the pin. He holed the putt.

The eagle, which Casey could only counter with a birdie, sounded the victory march. And if it wasn’t already over by then, a triple-bogey from the Englishman on the 12th meant the leading challenger’s chance had gone with the whins.

Oosthuizen, on the other hand, had birdied 12 to give himself the almost-unprecedented luxury of an eight-shot lead with six holes to play in The Open Championship. Undaunted and unflustered, he pressed on, making four consecutive pars and looking every inch the Champion. A bogey at 17 followed, but it was a controlled and calculated one.

And as he propelled another perfect, balanced drive down 18 his demeanor changed. Oosthuizen finally allowed the gravity of what he was achieving to dawn on him. He later explained that he knew that he wasn’t going to take 10 to get down from just short of the green — a small insight into the approach he had taken all week.

It would take a further three strokes for Louis Oosthuizen to seal his maiden Major Championship victory by seven, the largest winning margin at The Open since Tiger Woods won his first Claret Jug on the Old Course in 2000.

It certainly had not been the most dramatic final day in the history of the Championship, but those in attendance had the privilege of seeing a remarkable performance from a 27-year-old South African, who had led the world’s best as if it was the most natural thing in the world.