Victor Perez took advantage of a faltering finish from Matthew Southgate to clinch victory at the Alfred Dunhill Links Championship at St Andrews.
Southgate looked on course to claim his maiden professional title when he recovered from a bogey at the first with four birdies in five holes from the fifth, and his lead was two when Perez bogeyed the 11th.
But Southgate then duffed a chip at the long 14th and needed three more to get down as he ran up a bogey-six, and Perez seized the chance to tie the lead with four to play when he made a priceless birdie at the par-five.
The leading pair remained deadlocked until Southgate made another error at the iconic Road Hole 17th, where he produced an outstanding punch onto the green from the left rough only to three-putt from 50 feet to fritter away the lead heading to the last.
Southgate then over-hit his approach to the 18th green and left himself 25 feet beyond the flag while Perez, who was making only his 29th start on Tour, knocked his second to six feet to put one hand on the trophy.
The Englishman's birdie putt was good for pace but six inches too far to the left, and Perez took the two putts he had in hand to secure his first European Tour title with a closing 70 and a winning score of 22 under par.
"It's really hard to describe right now," said the Frenchman. "I feel like the emotions were really high all day, and it was really cold and windy out there. I felt like I was able to battle, but it wasn't easy because Matt played amazing.
"I was expecting some of the guys to charge, and we were fortunate in a it was a one-on-one battle on the back nine, and I was able to make that birdie on 14 that really pulled me back, and then just held strong till the end."
Perez also gave credit to his caddie JP Fitzgerald, who was on Rory McIlroy's bag for all four of his major victories before the pair split in 2017.
"Obviously JP knows the three courses, especially St Andrews," he added. "It was a huge advantage for me to know where to hit it and really trust him. He said from the get-go that his job was to tell me where I had hit it and my job was to execute, and I was able to do that today."
Southgate's consolation was his best finish of a "horrible season" that will go a long way to retaining his card for next season, and he said: "This has sorted that right out and got us right back to the Race to Dubai and that's the goal for me, really.
"I think I've proven to the world this week that when I do switch it on, I can mix it with the best and I've beaten a hell of a lot of good players this week."
Paul Waring matched his best result of the season after a solid 70 earned him a podium finish on 20 under alongside Sweden's Joakim Lagergren (69), while Tommy Fleetwood and Tom Lewis stormed into a tie for fifth after both carded superb rounds of 64.
Fleetwood started on the 10th and was level par after eight holes, but he then got hot with the putter and, after three birdies in four holes, he eagled the fifth and birdied the sixth, seventh, and ninth in a front-nine 29 that lifted him to 19 under par.
His hot finish also earned him and partner Ogden Phipps the team award ahead of Rory and Gerry McIlroy; both pairs finished level on 39 under, but Fleetwood's lower score in the main event proved the deciding factor.
McIlroy jnr came agonisingly close to helping his father celebrate his 60th birthday with some silverware as he birdied his final six holes to cap a 67 which left him seven strokes behind the champion.