That left Ryder Cup team-mate Sergio Garcia needing to par the same hole to win, but the 27-year-old took a bogey five and Harrington won the subsequent four-hole play-off by a shot to claim his first major title.

The 35-year-old Dubliner is only the second Irishman after Fred Daly in 1947 to lift the Claret Jug and Europe's first major winner since Paul Lawrie also triumphed in a play-off on the same course in 1999.

"I never let myself think I had blown the Open," Harrington said. "If I had lost I would have struggled to come back out and be a professional golfer. It meant that much to me. It would have been incredibly hard to take.

"If I'd lost I don't know what I'd think about playing golf again.

"But the 18th is the toughest finishing hole in golf. There's trouble everywhere you look. I knew it was going to be tough for Sergio to make par. He did hit a lovely putt and I thought he had holed it."

Instead it caught the edge of the hole and stayed out, and Harrington made the most of his reprieve.

"It's going to take a long time for it to settle in. There was so much going through my mind, some of it was genuine shock I had won the Open Championship," he added.

"It's going to mean a lot for Irish golf. We celebrate all our sporting achievements, we're a great country for anyone who does well. I'm very proud of the support I get at home. Far more people have more belief in me than I have in myself.

"It's important that I go and try to win another major rather than feeling this was the pinnacle. I'm going to celebrate like it was the pinnacle but I've got other goals now to move on with.

"I'm certainly going to enjoy this one for the foreseeable future. Forever actually."

Harrington won the Irish PGA in a play-off last week and also became the first home winner of the Irish Open in 25 years in a play-off in May.

Six behind Garcia overnight, he closed the gap with four birdies in 11 holes but admitted he did not feel it was his day until an eagle on the 14th.

"I got a lucky break there, I thought I was going to be 30ft away and it bounced down to 15ft," Harrington said. "At no stage before that did I feel everything was going my way.

"I missed a birdie putt on 16 and things like that are not a good omen."

Harrington still led by one playing the last however, but then drove into the Barry Burn and duffed his third shot into the water as well.

"I had 229 yards and was trying to aim left, with out of bounds left, and cut it back to the green," he added. "I hit it fat.

"But once I walked up there I felt I could get it up and down. I hit a lovely pitch and that was probably the most pressure-filled putt of the day."

Harrington fought back tears as he paid tribute to his late father during his winner's speech.

He pulled out of the Open at St Andrews in 2005 when his father Paddy - a former Garda - died from cancer days before the event.

"I'd like to thank my mum and dad. My dad is not here but I'm sure he is looking down," he said.