The 33-year-old Briton carded a closing 68 for a 20-under-par total of 268 to finish a stroke ahead of Swede Peter Hanson (69) and Spain’s Miguel Angel Jimenez (67) at the Royal Golf Club.

Casey and playing partner Hanson were tied on the 72nd tee and both players missed the green to the right with their approach shots.

Hanson splashed out to 10 feet after finding a greenside bunker and failed to sink his putt for a par four while the Englishman chipped to five feet from deep rough and holed out.

Casey’s victory was his first on the tour since he won the flagship PGA Championship at Wentworth in May 2009.

He will also climb to No. 5 in the world rankings unless Phil Mickelson finishes first or outright second at the San Diego Open later on Sunday.

Earlier, Denmark’s Soren Kjeldsen and Briton Richard Finch broke the course record at the Royal Golf Club.

The duo shot matching nine-under 63s to better by one stroke the 64 achieved by three players earlier this week.

Kjeldsen birdied his opening three holes and also the first three of his inward half to finish on 11-under 277.

“It was great as the last three days my golf had got worse and worse,” he told reporters. “I had a big session on the range yesterday and sort of figured it out after about an hour and a half.

“Today was just one of those days when I hit a good drive on the first hole, the driver had been my big problem, and I just felt happy after that.”

Englishman Finch raced to the turn in 29 thanks to an eagle and five birdies as he wound up on 276.

“I’m delighted with that score,” said Finch.