As Padraig Harrington prepared to take his tee shot on the 18th hole, he felt too warm and badly wanted to remove his sweater.

It stayed on. He wasn't going to do anything to disrupt the rhythm of his best ever round at the British Open.

Harrington's name was briefly back atop the Open leaderboard Sunday in shooting a 7-under 65 in the third round over a largely defenseless Old Course. It took him not just to 10-under par — two shots off the lead — but back to a career-changing period in 2007 and '08 when he won three majors — including two claret jugs.

"I'll be certainly telling myself that I know what I'm doing and I've done it before," the 43-year-old Harrington said about his mindset going into the final round Monday.

"I have no issue with putting my neck on the line and failing."

Those major-winning days seemed far away in November last year, when he dropped to 371st in the world rankings after missing the cut at the OHL Classic at Mayakoba.

Harrington knew he was a formidable opponent whenever he got in contention in a tournament, but that wasn't happening enough.

Winning the Honda Classic in March, to end more than six years without a victory, restored his confidence and he has brought that to the home of golf this week.

Harrington birdied four holes on the front nine to surge into contention Sunday and then picked up more strokes on Nos. 10 and 12. After a 40-foot putt crept in the side of the cup for birdie at the 16th hole, Harrington was tied for the lead on 10 under.

He never looked at a leaderboard the whole way round. Harrington knew he'd be up there the way he was playing and walked the last two holes with a beaming smile, parring his way home for a score he said he'd always wanted — a 65 on the Sunday of a British Open.

Harrington was last in contention to win a major in 2012, when he teed off at No. 18 still with a chance.

"It's more important to be consistent, but who cares about consistent," Harrington said, quickly correcting himself. "It's more important to be erratic and win.

"I've been out of it for a while but I felt very comfortable with myself out there today."

Harrington, who won the U.S. PGA Championship in 2008, has missed the cut three times and hasn't placed higher than tied for 39th at the British Open since lifting his second claret jug in 2008 at Royal Birkdale.

His previous lowest round at an Open was 66 at Royal Lytham in 2001.