Sandwich: Thomas Bjorn took his revenge on Royal St George's as the British Open got underway on Thursday, eight years after he blew his best chance of winning golf's most glittering prize.

The 40-year-old Dane stormed to a five-under-par 65, with seven birdies against two bogeys, to take the early clubhouse lead, as favourite Rory McIlroy got off to a rocky start with two bogeys in his first three holes.

Bjorn is best known for blowing a three-stroke lead with four to play the last time the Open was held at Sandwich in 2003.

Struggling for form of late, he was only sixth reserve for this year's tournament as recently as last week before a spate of withdrawals, but made the most of his call-up on Monday when Vijay Singh pulled out through injury.

After saving par from over the green on the downwind first, Bjorn holed from 14 feet for a birdie on the second and almost repeated the trick from twice the distance on the third.

The former Ryder Cup player then saved par on the next two holes with good chips to three and six feet respectively, missed from eight feet for birdie on the sixth but holed from five feet for birdie on the par-five seventh.

He bogeyed the ninth, but then charged down the back nine in three under par as the gallery following him grew hole by hole.

Behind him McIlroy's quest for a US/British Open double got off to a troubling start.

The 22-year-old from Northern Ireland won the US Open by a stunning eight strokes last month to make the move from golfing prodigy to superstar status, and in the absence of the injured Tiger Woods, he is the biggest draw at the 140th Open.

McIlroy was watched by a sizeable and admiring gallery as he set off at 9:09 am in the company of 2002 champion Ernie Els of South Africa and American hope Rickie Fowler.

In cool, cloudy conditions, with just a slight breeze blowing, the Ulsterman, seeking to become the youngest winner of the Open since 1893, clobbered his opening drive safely up the fairway of the 444-yard, par four opening hole.

But after over-hitting his approach, McIlroy three-putted from just off the back of the green.

He then overhit his tee-shot at the long, par-three third and again needed three from the back of the green to drop to two over where he stayed through six.

He grabbed his first birdie at the eighth though to reach the turn in one over 36.

It was the first time McIlroy had played competitively since winning in the United States, but he insists he can cope with the spotlight as he attempts to become the first player to win the US and British Opens since Woods in 2000.

Early scores in the clubhouse at two under were Simon Dyson of England with another Englishman, Danny Willett, and American veteran Marc Calcavecchia, who won his only Major at Troon in 1989, signing for one under.

"It wasn't as windy as it has been the last few days, but it's still blowing pretty hard out there," Calcavecchia said of the conditions.

"This type of golf requires a huge amount of imagination, you need to see the shots you want to hit.....I really like this course, even though it's a little quirky. It's fun."

World No.1 Luke Donald, seeking to provide the first English win in the Open since Nick Faldo in 1992 looked on song with a birdie at the third.

He bogeyed the sixth but got back into the red at the following hole by sinking a monster putt and was out in one-under 34.

At 7,211 yards and a par of 70, bumpy, quirky Royal St George's on a flat stretch of Kent coastline is a tough test for the world's best and one that will get even tougher if the offshore winds blast inland over the next four days.

In the absence of Woods, four-time major winner Phil Mickelson will be expected to lead the way for the Americans, seeking to end a record run of five Majors without a US winner.

He had a mid-afternoon tee-off time in the company of defending champion Louis Oosthuizen of South Africa and reigning PGA champion Martin Kaymer of Germany.