Phil Mickelson called his final-round 66 to win his first Open Championship at Muirfield "the round of my life".
The American, 43, was five shots off the lead overnight but carded the week's low round to win by three.
"This is such an accomplishment because I never knew if I'd be able to develop my game to play links golf," said Mickelson, winner of five major titles.
"I never knew whether I would be equipped, have the shots, have the opportunity to do this."
Mickelson was seemingly on the periphery when a front nine of 34 was followed by a bogey on the 10th, but he birdied the 13th, 14th, 17th and 18th to take the clubhouse lead.
He ended up winning by three shots from Sweden's Henrik Stenson, with English pair Ian Poulter and Lee Westwood four back, alongside Australia's Masters champion Adam Scott, and world number one Tiger Woods another shot back.
The victory moves Mickelson back to number two in the world for the first time since September 2010.
And with three Masters and a US PGA title already to his name, he only needs to win a US Open to complete a career Grand Slam.
"We had such firm, fast conditions here, the epitome of links golf, to putt better than I've ever putted, to shoot the round of my life feels amazing," said Mickelson, who moved into the lead with two holes left in his round.
"When I made that putt on the 13th to get back to level par I thought that would be a score that was going to contend and have a great opportunity to win - and I made some great putts coming in.
"I knew that it was so difficult coming down the stretch that having to make birdies to chase somebody down would be extremely difficult.
"The range of emotions I feel are as far apart as possible after such a difficult loss at the US Open [Mickelson recorded a record sixth runner-up spot in the US Open behind Justin Rose last month].
"You have to be resilient in this game, you have to accept losses and use it as motivation to work harder and come back strong rather than letting it defeat you."
Mickelson's coach Butch Harmon called his charge's performance on Sunday as "the best round of golf I've seen".
"I said when Greg Norman won in 1993 that that was the best round of golf I've seen, but I think this one tops it," said Harmon, who has now coached four Open champions.
"Today the wind blew harder than it has and to go around when you knew you had to do it is absolutely brilliant.
"It took him a long time to understand how to play links golf. Phil plays very aggressive, but you can't do that with links golf. He just embraced how to play on links."
Mickelson's long-time caddie Jim 'Bones' Mackay commented on the serenity of his employer as the tournament entered its final stages.
"He did seem to be really at peace today and very confident with what was going on," said Mackay, who has been on Mickelson's bag since 1992.
"To go from where he was to the top of the leaderboard he had to be very calm. He knew he was putting great and putting himself into a position to succeed out there.
"I think it ranks right up there among his previous wins. I love the Masters but I love the British Open, especially in Scotland. It means the world, for me as his caddie at least, to win - it's very special."
Phil's wife, Amy, told BBC Sport: "He's been very calm, he's been enjoying it so much and he always seems to play well when he's having fun.
"He was very confident this morning, relaxed, and excited for the day. He said 'I'm going to bring you home a Claret Jug'. I always have confidence in him but he was especially relaxed today."