Tyrrell Hatton equaled the course record at St. Andrews to take control of the Alfred Dunhill Links Championship on Saturday.
The English golfer carded 10 birdies in a flawless 62 on the Old Course, and will take a three-shot lead over compatriot Ross Fisher into Sunday's final round at the same venue, one of three used for the pro-am event.
Hatton, ranked 53 in the world, finished 17 under par in pursuit of his first European Tour title.
"(It's) quite clearly the best round I've ever had," Hatton said. "My bad shots, I didn't really get punished for them. I missed them in good spots and I just putted really well. If you are holing putts, you're always going to shoot a decent score.
"The putt on 17 was probably the best putt I holed today, 25 feet. But the majority of them were around six to 15 feet and if you keep knocking them in, it's certainly good for confidence."
Fisher, the halfway leader who lost a playoff for the European Open last month, carded a 69 at Carnoustie to finish 14 under, with South Africa's Richard Sterne and Sweden's Joakim Lagergren a shot further back.
"Hopefully, I'll be drawn with Tyrrell (on Sunday), because we're pretty good friends," Fisher said. "We've spent quite a few evenings together for dinner and stuff.
"I'm sure we'll go out there and have some fun and put on some good golf for the public and, you know, whether it's me, him, someone else, there's going to be a worthy winner come tomorrow afternoon."
Martin Kaymer is five shots off the lead after a 65 on the Old Course, but he was more concerned with making the cut in the team event with his father Horst.
"I know how hard he's trying, and we played the last few years and we always came one shot short," Kaymer said. "He never experienced the final round at St. Andrews, so the most important thing is that we have a good time out there as a family."