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 and then 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.
Sanders said: "I made a hash of it in the Oaks Trial, but that was a trial.
"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."
O'Brien said in the immediate aftermath: "I'd be lying if I was to give you an accurate reflection of how they have all run right now, but I can tell you the second filly has run a great race."
Murtagh said of his mount: "She emptied pretty badly coming down the hill and I thought she would have stuck on more."
John Oxx said of Katiyra: "She ran well. She was impeded a little bit coming down the hill when she was caught up in traffic.
"She stumbled crossing the road, which maybe cost her second, but then she quickened up well, despite her inexperience.
"The trip was always going to be an issue but she seemed to get it OK and I expect she'll run next in the Irish Oaks in five weeks' time."
Beckett was left almost speechless as Look Here shocked the big guns. The filly had only raced twice previously, first time beating Derby fancy Doctor Fremantle in a maiden as a two-year-old and then finishing second in the Lingfield Oaks Trial on her reappearance this season.
Sanders was ultra critical of himself for getting beaten on that occasion, but he got his act together when it mattered most.
After regaining his composure, Beckett said: "I must apologise to anyone stood next to me towards the finish and I'm glad the cameras were not on me!
"This is just amazing, you do not expect to win races like this when you start training. When she hit the front I was looking around for dangers and willing her on, it is just an amazing feeling. She had only done two pieces before running at the end of last season and had only worked once on grass.
"We left her alone after she had worked and it got to the point where we had to run her. I was at the sales in Ireland, but it looked a good solid race. She is best fresh and I was worried about the time between Lingfield and here and given she is best fresh, we will wait and see how she is before making any plans. But my immediate reaction would be to say she won't go to the Irish Oaks as I don't want to travel her at this stage."