Australian Adam Scott has taken the lead midway through the final round of the British Open at Muirfield.

After a tough opening, a run of four birdies in five holes lifted the Australian world No.4 into prime position to challenge for a second major title.

After 11 holes, Masters champion Scott sits at two-under for the tournament, one ahead of overnight leader Lee Westwood and a surging Phil Mickelson.

Englishman Westwood held a two-shot lead coming into the final round but slipped back with two straight bogeys on the seventh and eighth holes.

He and Mickelson were one stroke ahead of American Zach Johnson, while Tiger Woods was four shots off the pace.

Englishman Ian Poulter grabbed the clubhouse lead, coming from back in the pack lead with an impressive 67 to sit at one-over par for the tournament.

Australian Jason Day was well out of the hunt at eight-over par late in his round, while Geoff Ogilvy (+10), Marcus Fraser (+11) and Peter Senior (+16) were in the clubhouse.

Scott, who in April became the first Australian to win the Masters, is seeking redemption after a dramatic final-round collapse at last year’s Open.

He led by four shots with as many holes to go, only to collapse and allow South African Ernie Els to steal the title.

Scott is aiming to become the first Australian to win the British Open since Greg Norman in 1993.

The 33-year-old’s final round got off to a difficult start when he found a nasty bunker with his opening tee shot.

He did well to escape with a bogey but dropped another shot on the par-3 fourth, the most difficult hole on the course.

Scott’s broomstick putter finally warmed up when he made birdie at the seventh hole before he dropped a monster 40-foot putt on the eight to climb back into third on the leaderboard.

A superb approach into the par-five 9th hole set up a makeable eagle putt, but he left it just short.

Scott seized the outright lead on the 11th hole, almost hitting the flag with his approach before sinking a relatively simple birdie putt.