How do you define a giant-slayer, someone capable of humbling the world's number two golfer? What do you say about somebody who can jump from obscurity, and who wasn't even in the field until Tiger Woods pulled out, and manage to outplay Ernie Els - on a course where he is the undisputed king - in the final round of the Dubai Desert Classic?

Perhaps it is best simply to hail Robert-Jan Derksen, a player who has never managed to keep his tour card in five seasons as a professional, after the Dutchman yesterday proved that nobody is truly infallible on a golf course.

While most people expected Els to continue on his winning ways, Derksen took destiny in his hands and shot a final round 65 to leapfrog six players from his final day's starting position and claim the title.

Ironically, Derksen can thank Woods for the chance to overcome the odds. He was first reserve last Sunday when Woods made the decision to withdraw. His total of 17-under-par 271 gave him a one-stroke margin over Els.

Maybe Els will point to how the 18th hole proved to be a foe rather than a friend. It's a par five of 547 yards, seemingly tailor-made for the South African's overpowering game, yet he finished one-over-par for that hole over the four days, while Derksen played it in two-under.

"He came out of the pack, and beat me. He played well, it is one of those things," said Els.

In truth, though, Dersken - wiping away tears as he walked off the final green having set the clubhouse mark for Els three groups behind - played winning golf more typical of someone who had been through it all before. His round contained five birdies, including one on the final hole, and an eagle, which came on the 13th, where he holed an unlikely putt of almost 80 feet. And there were no dropped shots.

In contrast, Els double-bogeyed the 12th, when his seven-iron approach from the first cut flew the green, and then, after hitting a huge drive and requiring just a five-iron approach, he failed to birdie the last to force a play-off.

"I was conscious of the re-ranking coming up in five or six weeks, and knew it was important to make some money," said Derksen, a graduate of last year's tour school but had travelled to South Africa and Singapore as first reserve without getting into either tournament. "Now I don't have to worry about such things."

Derksen, a product of the Dutch amateur coaching system, where Irish-born Tom O'Mahoney was his coach, didn't put a foot wrong in securing his first career title as a professional. The 29-year-old, whose previous best finish was tied-12th in the 2001 North West of Ireland Open, moved from 193rd in the Order of Merit to sixth and became the fifth first-time winner on the European Tour this season.

If Derksen won, then the most majestic golf was played by Darren Clarke, who finished with a 66 for 11-under-par 277 and tied for 11th. There was a time in the past when a sequence of bogey-double-bogey, as happened at his ninth and 10th holes, would have led to a white flag being held aloft. His response to those drawbacks was to go on a blitz that saw him birdie every hole from the 13th home.

Indeed, the dropped shots would have broken many hearts. The first, on the ninth, came when he hit a 320-plus-yard drive that landed on the fairway but hit a sprinkler head and bounded off into the water; the double bogey came after his drive was hit marginally right but received such a huge kick that it bounced out of bounds.

His reply, if not instant, didn't take long. Clarke chipped dead for a birdie on the 13th; hit a nine-iron to 20 feet on the 14th; hit a seven-iron to 40 feet on the 15th and, wonder of wonders, holed a long putt; holed from 10 feet on the 16th; drove the green on the 359 yards 17th and two-putted for birdie, and finished off by hitting a four-iron approach of 196 yards to 12 feet on the last, leaving the eagle putt on the lip.

Peter Lawrie, meanwhile, struggled with his driving in the final round and finished with a 73 for seven-under-par 281. It gave him his biggest pay cheque on tour, for €19,030, and moved him from 132nd to 79th on the Order of Merit, but there was a large measure of disappointment with his performance.

"This is all part of the learning process," he admitted. "I made a poor start, got behind the eight-ball early on, and struggled after that."

For Padraig Harrington, a disappointing week finished with a 71 for three-under-par 285, the same mark as Paul McGinley, who confessed that Saturday's third round, which included one four-putt and three three-putts, was "probably the worst putting I've ever had on tour". He blamed taking antibiotic tablets, for a lingering chest infection, for upsetting his rhythm.

Harrington spent five hours on the range on Saturday evening trying to cure a swing he described as "wooden." And there were signs yesterday that his game is coming back, if not completely.

"I'm actually happy with the way I'm swinging the club but practice is different from tournament play and I need to get my sharpness back by playing in tournaments. I'm hitting the ball hard and, when I do that, I'm inclined to take a bit of a lunge."