Tyrrell Hatton surged five shots clear in his defence of the Alfred Dunhill Links Championship after carding another bogey-free 65 at Kingsbarns.
The Englishman repeated his fine second-round showing to take control in his bid to become the first back-to-back winner in the tournament's 17-year history.
Level with Tommy Fleetwood at the top of the leaderboard at the start of day three, the 2016 winner birdied three of his first five holes and finished at 18 under-par overall.
Four-time European Tour winner Gregory Bourdy posted four consecutive birdies on his back nine at Carnoustie to sit second, with British Masters winner Paul Dunne two shots behind him in third.
After setting a course-record 63 at Carnoustie on Friday, Fleetwood came crashing back to the pack following a four-over 76 at Kingsbarns.
With a strong lead heading into the final round, Hatton is eager to make history at St Andrews.
"To win at the home of golf once is incredible but to do it again and defend would be a dream come true," Hatton said.
"Last year was a new experience for me going out leading a tournament and I managed to do a really good job. Made myself very difficult to catch, hopefully I can do that again tomorrow."