Trainer Ralph Beckett and jockey Seb Sanders landed their first British Classic as Look Here produced a 33-1 shock in the Juddmonte Oaks at Epsom.
Runner-up in the Lingfield Oaks Trial on her only other start this year, the Hernando filly sprinted clear of her rivals two furlongs out and the race was over as a contest.
Moonstone (25-1) made late headway for Richard Hughes to claim second three and three-quarter lengths away, with Katiyra, who seemingly failed to handle Tattenham Corner, back in third.
Johnny Murtagh tried to make all the running on Adored, his choice of the six Aidan O'Brien runners, but was soon swallowed up in the straight.
The Irish still looked set to fight out the finish as first Chinese White andthen Lush Lashes laid down a challenge.
But nothing could get near Look Here as Sanders, joint-champion jockey with Jamie Spencer last season, rode her out to the line for a famous victory.
Frankie Dettori's mount Clowance ran on for fourth with Lush Lashes fading to fifth.
"I made a hash of it in the Oaks Trial, but that was a trial," Sanders said afterwards. "I found out a lot about her that day because I made a mistake.
"I've come here today and no-one has asked me anything about her, but deep down I knew she'd run a massive race because she gave me a lovely feel at Lingfield."
Earlier, Ballydoyle got the Classic weekend off to a perfect start when Soldier Of Fortune (9-4) landed the Juddmonte Coronation Cup.
Last year's Irish Derby winner had the assistance of two pacemakers and after Song Of Hiawatha dropped away, Ormonde Stakes winner Macarthur made a bid for home.
Hot favourite Getaway moved up to challenge but as Soldier Of Fortune quickened for Johnny Murtagh, the 5-4 market leader had nowhere to go.
However, the French challenger was starting to tread water anyway and it was Mick Channon's Youmzain who flew from the clouds to claim second, three-quarters of a length away, with Macarthur third and Papal Bull fourth.
O'Brien said: "He's a natural horse and he's strengthened up since last year.
"It was a level pace, but it was not that strong because Frankie (Dettori, Red Rocks) pulled the field back off them (Song Of Hiawatha and Macarthur), he made it into a different race and I didn't believe they could get there.
"Macarthur is a very good horse and he had gone. He (the winner) was entitled to get tired with it being his first run of the year, but he just got there. He's an exceptional horse."