Darren Clarke wins the 2011 Open Championship

SANDWICH, England (AP) -- Darren Clarke gave little Northern Ireland another big championship Sunday at the Open Championship.

The 42-year-old came into the week as an afterthought, but three straight scores in the 60s and a par 70 in the final round lifted him to a comfortable three-stroke victory over Americans Dustin Johnson and Phil Mickelson.

Mickelson made an impressive charge on the front side, actually moving into a share of the lead with an eagle at No. 7. But Clarke came along and put up an eagle of his own at the same hole, then watched Mickelson fade down the stretch for a 68.

Clarke won his first major championship with a 5-under 275, following the path of younger countrymen Rory McIlroy and Graeme McDowell. They won the last two U.S. Opens.

No one could've seen this coming. It had been a decade since Clarke was a serious contender in a Grand Slam event, and the one-time face of Northern Ireland golf was thought to be long past his prime.

Well, he showed the kids a thing or two at wet and windy Royal St. George's.

"I always believed I would get myself back up here," Clarke said. "I always believed I had enough talent to challenge and win one."

The victory was especially poignant given Clarke's difficulties off the course. His wife, Heather, died in 2006 after a long battle with breast cancer. Clarke teared up as he remembered her.

"Somebody up there," he said, glancing toward the sky as he collected the Claret Jug, "is watching down as well."

Johnson was within two strokes of the lead when he made a huge blunder, knocking an iron shot out of bounds from the 14th fairway. He wound taking a double bogey that ended his chances, another disappointment playing in the final group of a major.

Johnson settled for a 72, leaving him tied with Mickelson at 278.

Last year, Johnson threw away a lead at the U.S. Open with a closing 82, and he will forever be remembered for taking a two-stroke penalty of the 72nd hole of the PGA Championship to miss out on a playoff.

Beginning the day five strokes behind Clarke, Mickelson surged up the leaderboard with a brilliant start, even as the wind gusted to more than 30 mph and frequent spurts of heavy rain pelted the seaside course.

Lefty made three birdies in the first six holes, pumping his fist as the ball kept dropping in the cup. Then he rolled in a 25-footer for eagle at the seventh, moving into a share of the lead.

Clarke didn't falter. Coming along four groups later in the final pairing, the Ulsterman rolled in a 20-foot eagle at the seventh, reclaiming a two-stroke edge. He never gave it up.

Mickelson went out in 30 and made another birdie at the 10th, then was bitten by a familiar bugaboo: a 2-footer lipped out at the 11th to give him his first bogey. He made three more bogeys before slamming his approach off the grandstands at the 18th.

Johnson, who played with Clarke in the final pairing, re-emerged as Clarke's main challenger with two birdies at the beginning of the inward nine.

Then, from the middle of the fairway at the par-5 14th, Johnson made the sort of mistake for which he is becoming known. He inexplicably knocked the ball out of bounds with a 2-iron. That led to a double bogey and, suddenly, Clarke's lead had gone from a tenuous two strokes to a commanding four.