But Stenson, who finished second behind Mickelson in the 2013 Open at Muirfield, then three-putted the sixth and failed to get up and down from a bunker on the eighth, which was playing just 100 yards after the tee was moved forward in anticipation of strong winds.

Mickelson was left cursing the "golfing gods" after his birdie putt to shoot the first 62 in major history lipped out on Thursday, but received a massive stroke of luck on the 12th.

A badly sliced tee shot was headed deep into trouble but bounced off a gorse bush and into a position from where the left-hander was able to hack out down the fairway.

Mickelson's approach to the green then span back around 15 feet and caught a down slope which took it closer to the hole, from where he holed for the most unlikely of pars to remain a shot in front.

A birdie from 25 feet on the 13th doubled Mickelson's advantage but the 46-year-old lost it immediately by three-putting the 14th after Stenson had holed from four feet for birdie.

That left the pair tied for the lead on 11 under par and five shots clear of American Bill Haas, with England's Andrew Johnston another shot back following a 70.

With winds forecast to reach speeds of 30mph, tournament organisers had opted not to cut or roll the greens and moved tees forward on the eighth, 11th, 16th and 17th, although Jordan Spieth felt the last two changes were "unnecessary".

"I don't think that did anything to it," Spieth said after a disappointing 72 left him five over par. "But the one on eight is pretty cool so it's under 100 yards now and you're trying to figure out what club to hit and how to hit it, where to hit it, almost where to lay up.

"For how strong the wind was when we were on the tee, I thought that was a great set-up."