Lee Westwood held off Tiger Woods to take a two-shot lead into the final round of the 142nd Open Championship at Muirfield.
The pair duelled on an absorbing afternoon in the Scottish sun, but Westwood held firm to fire 70 and finish three under.
Woods faltered at the 17th and carded 72 to end one under alongside fellow American Hunter Mahan, who shot 68, as overnight leader Miguel Angel Jimenez fell away with a 77.
Masters champion Adam Scott, runner-up to Ernie Els at Royal Lytham last year after blowing a four-shot lead over the final four holes, inched to level par on his own with a one-under 70.
The sun-baked course and testing wind were not the only difficulties on the shores of the Firth of Forth as tournament timekeepers clamped down on slow play.
A number of groups were put on the clock, including the final pairings of Woods and Westwood and Jimenez and Stenson, while Japan's Hideki Maruyama was penalised a shot for two slow-play warnings.
But the timekeeping issue was a sideshow to the drama in the penultimate group, which consisted of world number 12 Westwood and top-ranked Woods.
The duo began the day two under, one shot off the pace of Jimenez, but the duel ignited on the long fifth when Westwood took a driver off the fairway for his second shot and then holed a long, curving, rolling putt from off the front of the green for an eagle to take the lead.
A Westwood birdie to a scrappy Woods bogey from over the back at the short seventh gave the Englishman a three-shot lead, but the pair were level again after a Woods birdie at the ninth.
The 40-year-old Westwood stuck his nose in front at three under with a birdie on the 14th but pulled his tee shot into thick rough on the short 16th and could only hack out short of the green. He putted up the bank to 15 feet, but crucially slotted the putt to escape with just a bogey to slip back alongside the American.
But when Woods found a bunker and made a scruffy bogey on the long 17th to Westwood's birdie, the Florida-based Englishman was back in front by two from Woods and clubhouse leader Mahan.
Two pars up the last put Westwood in pole position to clinch his maiden major at the 62nd attempt. Westwood, who has had seven top-three finishes at majors in the past five years, was second at the Open at St Andrews in 2010, third at Turnberry in 2009 and fourth at Troon in 2004.
Woods, who is chasing a 15th major and a first since 2008, has never won a major when trailing going into the final day.
"I was trying to grind along and play my own game, regardless of what Lee was doing or what anyone else was doing," he said. "This golf course is a tough test and I was just trying to execute my own game plan. And wherever that ended up, it ended up.
"I'm pleased where I'm at; I'm only two back. There's only one guy ahead of me.
"But it's not just us two. There's a bunch of guys who have a chance to win this tournament. And all of us need to really play well on Sunday to win it."
"My emotions were pretty calm all day," said Westwood. "I just tried to stick to my game plan and try not to get into too much trouble. And I made putts when I needed to. The only time I let out any emotion was the eagle on the fifth, I gave a little fist pump there."
Argentina's double major winner Angel Cabrera (73), first-round leader and 2007 Masters champion Zach Johnson (73), fellow American Ryan Moore (72) and Sweden's Henrik Stenson (74) were tied on one over.
Phil Mickelson climbed to one under after 12 holes but gave away shots at the three of the next four holes for a 72 to end two over alongside Italy's Francesco Molinari (72).
Spain's Sergio Garcia found some form with a 68 to climb to three over alongside Matsuyama (72), American Brandt Snedeker (69), who led after the second round last year, Wales' Jamie Donaldson (71) and Australian Jason Day (72).
Els carded a one-under 70 to end five over but will be mindful of last year when he came from six strokes back on the final day to overhaul Scott.
"Somebody can get hot, and if the leaders don't get hot, you're in the ballgame," said Els, who won at Muirfield back in 2002.
"That's what I'm hoping for. It's tough when you've won and had a lot of things going your way and then the next year you don't get the bounces. But that's links golf. I'm a competitor. You're not going to lie down until the 72nd hole."
Scotland's Martin Laird edged to within one of the lead before a quintuple bogey nine on the third dented his challenge. Three further bogeys, a double and a triple scuppered his chances completely as he ran up an 81 for nine over.