Ouija Broad, ridden by Olivier Peslier, made a late burst to win Wednesday's feature race at Royal Ascot - the Prince Of Wales's Stakes.
Olivier Peslier celebrates his Prince of Wales Stakes win on Ouija Board
Ed Dunlop's star mare, who was second to Shirocco at Epsom in the Coronation Cup, sprinted clear to land the Group One contest over a mile and a quarter.
Godolphin's Dubai World Cup-winner Electrocutionist, ridden by Frankie Dettori, was second with Manduro third.
Pre-race favourite David Junior finished a disappointing fourth.
Dettori had set a steady pace on Electrocutionist, leading from Manduro and Notnowcato.
He still led turning for home, where David Junior looked dangerous only for his challenge to soon falter.
And once Peslier switched Ouija Board to the outside, his ride quickly stamped her authority, mowing down her rivals in the final half-furlong to capture her fifth success at the highest level for owner Lord Derby.
Olivier gave her a great ride and I always knew she could quicken.
Ouija Board's trainer Ed Dunlop
Peslier said: "There weren't many runners and the race was not run very fast.
"This filly has a good turn of foot. It took a little time before I got out but after that she changed her legs and got going. Then I knew I was going to get there."
The horse's trainer, Ed Dunlop, told BBC Sport: "Olivier gave her a great ride and I always knew she could quicken.
"She can quicken against the best and she's proved that. This was probably the best run of her life."
Second-placed jockey Dettori said of Electrocutionist: "He ran great. We tried to stretch their stamina and he had everything beat, bar the good mare.
"It was a super run after a lay-off, he gave me a lovely feel and he will be a live contender for the King George."