Hot favourite So You Think suffered a shock defeat as Frankie Dettori on Rewilding won the Prince of Wales's Stakes at Royal Ascot.
Dettori produced a determined ride to claim victory as he reeled in the long-time leader with his 17-2 chance.
The shine was taken off the victory, however, when - 24 times in the final two furlongs.
The imposing Australian import So You Think, now trained in Ireland by Aidan O'Brien, burst into the lead and charged clear but had his bubble burst by Rewilding.
Dettori timed his run brilliantly and triumphed by a neck from the 4-11 favourite.
So You Think went into the race with positive vibes from O'Brien about the "very special" horse he has trained since he was sent to his Ballydoyle yard after finishing third in the Melbourne Cup in November.
Stablemate Jan Vermeer set the pace, and with echoes of Frankel's winning display on Tuesday, the favourite set off in early pursuit.
Three-time champion jockey Ryan Moore looked to have settled matters as five-year-old So You Think cruised to the front with a powerful injection of pace.
Dettori had other ideas and got to work on Rewilding, who was third in the 2010 Epsom Derby to Workforce.
And he edged past in the Dubai royal blue colours of Godolphin, with runner-up So You Think six lengths ahead of Sri Putra in third.
The four-year-old winner had been sixth in last season's St Leger over a mile and three quarters, but he relished this trip over half a mile shorter.
It was another memorable triumph for Dettori, the Italian-born rider who claimed a famous Magnificent Seven victories at this course in 1996.
He celebrated with a trademark flying dismount after scoring his 44th Royal Ascot victory to cement his place as the current rider with the most career wins at the meeting.
"He never gave up," said Dettori. "It was a tremendous battle between two great horses.
"When I got past [So You Think] it was sheer joy - it was a privilege to be in such a great race.
"I'm delighted for Rewilding. He doesn't get the recognition he deserves, he's a very good horse and he showed his true colours today."
So You Think trainer Aidan O'Brien, meanwhile, took the blame for his horse's performance, saying: "I will take responsibility for this personally.
"Frankie gave his horse a beautiful ride, on a horse that stays a mile and a half well, he just came and got him in the last 50 yards.
"I think it was trainer error, I didn't have him fit enough for this kind of race and he's given a good blow afterwards.
"I would think there's improvement to come."
Earlier, Strong Suit bounced right back to his best to win the Jersey Stakes, the opening event on the second day
Winner of the Coventry Stakes last year, the Richard Hannon-trained colt had failed to build on the win and underwent a breathing operation after disappointing behind Frankel in the Greenham Stakes - leading to starting odds of 11-1.
He was carrying a penalty for his win at the Royal meeting 12 months ago, but easily caught the front-running Utley still on the bridle and quickened clear.
The well-backed favourite Codemaster came through the pack to give chase but Richard Hughes was always holding him and prevailed by half a length. Jeremy Noseda's Western Aristocrat flew home for third.
There was also a surprise result in the Windsor Forest Stakes, with another 11-1 shot Lolly for Dolly, ridden by Wayne Lordan, leading Chachamaidee and First City past the winning post.
Favourite Sajjhaa, ridden by Frankie Dettori, came home in fourth.
In the later races, Eddie Ahern rode 12-1 shot Julienas to victory in the Royal Hunt Cup ahead of Dance and Dance, Invisible Man and Pendragon.
In the Queen Mary Stakes, Richard Hughes led Best Terms to victory by a short head ahead of 6-5 favourite Shumoos in a photo finish, with Caledonian Lady third and Fire Lily fourth.
And in the Sandringham Handicap, Rhythm of Light finished ahead of Kieren Fallon's joint favourite Dubai Queen, Winter's Night and Cape Dollar.
The Queen's horse Humdrum, however, could only manage fifth.