Ouija Board romped to a seven-length victory in the Oaks at Epsom.
Jockey Kieren Fallon produced his mount from two furlongs out to overhaul the Aidan O'Brien-trained All Too Beautiful, sent off favourite.
Fallon's 7-2 shot, trained by Ed Dunlop, streaked away from the field to leave All Too Beautiful and Punctilious trailing in her wake.
Frankie Dettori's partner Punctilious got the better of more-fancied Godolphin stable-mate Sundrop.
Ouija Board was given a superb ride by Fallon to hand the filly's owner Lord Derby and Dunlop a first English Classic winner.
The champion jockey settled his mount in the rear of the field as Kisses For Me set the early pace, with Dettori soon taking it up on Punctilious to step up the pace.
Sundrop pulled hard under Kerrin McEvoy all the way and she soon faded out of it turning for home as Dettori kicked on.
All Too Beautiful was poised on the outside and Jamie Spencer delivered her for a winning run, but he had no answer to Fallon, who was biding his time before throwing down his challenge.
But once the daughter of Cape Cross changed gears, she sailed home to give Fallon his third Oaks success.
"We didn't know whether she would stay, but Kieren gave her a great ride, she got home well and won like a champion," admitted Dunlop.
"I watched my father John train a Classic winner but to do it myself is amazing."