Jordan Spieth has stolen Branden Grace's thunder to take command of the British Open and close in on his own slice of golf history at Royal Birkdale.
Grace became the first man in major championship history to shoot 62 with a magical eight-under-par round as golf's biggest names upped the ante in pursuit of the coveted Claret Jug.
But Spieth stood firm, extending his halfway lead to three strokes with a nerveless, bogey-free five-under 65 to continue his march towards a rare career slam.
The 2015 Masters and US Open winner - and reigning Australian Open champion - is three clear of Ryder Cup teammate Matt Kuchar, whose rollercoaster round of 66 ensured the duo would stoush again in Sunday's final group.
Fellow American and newly crowned US Open champion Brooks Koepka (68) shares third with 20-year-old Canadian Austin Connelly (66) - but five shots adrift of the relentless Spieth.
Grace soared from four-over to four-under for the championship to be equal fifth with world number two Hideki Matsuyama (66) as golf's elite had benign Birkdale under siege.
World number one Dustin Johnson, with a brilliant 64, is tied seventh with defending champion Henrik Stenson (65), unfancied Chan Kim (67) and Scottish Open winner Rafael Cabrera-Bello (67).
Superstar Rory McIlroy rounds out the heavyweight leaderboard at two-under after blowing a flying start in a crowd-teasing 69, while Australians Jason Day and Scott Hend are equal 18th after carding 65s.
A victory on Sunday - after the 23-year-old fell one shot shy of a play-off at St Andrews in 2015 - would make Spieth only the second player after Jack Nicklaus to have won three of the sport's four majors before the age of 24.
"That would be incredible," Spieth said.
"I've had a five-shot lead in a major and squandered it before. I've had the high and the humbling, so I will keep my head down and not get ahead of myself."
But if he does get his hands on the Claret Jug, Spieth could then surpass the record of Tiger Woods as the youngest player to complete a career grand slam at next month's US PGA Championship at Quail Hollow.
The bad news for the chasing pack is that Spieth has converted five of his last six 36-hole leads into victories.
The good news could be that the exception was last year's Masters, where he blew that five-shot lead with just nine holes to play as Englishman Danny Willett stole the green jacket.