Loving Dream caused an 18-1 upset for John and Thady Gosden and jockey Robert Havlin in the Ribblesdale Stakes at Royal Ascot.
The apparent second-string from the Gosden yard given Frankie Dettori was on Gloria Mundi, the daughter of Gleneagles took a huge step forward from her fifth place in the Lingfield Oaks Trial.
Running in the famous pink colours of Lordship Stud, she hit the front a long way out and there were plenty of challengers queueing up behind her.
Deep inside the final furlong it was Roger Varian's previously unbeaten Eshaada who broke free of the pack deep inside the final furlong to throw down the biggest challenge.
However, to Loving Dream's credit she found more for pressure and held on to win by three-quarters of a length.
Aidan O'Brien's pair of Nicest and Divinely were third and fourth while Noon Star, who beat the winner at Wetherby earlier in the season, was forced wide into the straight and finished unplaced.
It was just a second win at the meeting for Havlin after Ardad's victory in the Windsor Castle in 2016.
He said: "They're (races at the Royal meeting) not easy to win, the same people seem to win them every year!
"It's great to ride another one, especially for the boss, and the filly has done well. I thought she was overpriced on the day and that has been proven to be so.
"She was drawn 12 so my hand was forced, we thought there was probably going to be early pace and then it would settle down, so if I tried to get a mid-div position I would have been caught wide, so myself and William (Buick, on Dubai Fountain) just kept forward and kept kicking until we got there.
"Luckily we got a nice break and saved plenty for the straight."
He added: "It's fantastic. Yesterday I had a ride for Her Majesty (Pied Piper, 10th in the Queen's Vase), we didn't do too well but that was another childhood dream so I'm ticking the boxes.
"I'm getting on in my career so I can enjoy them a little bit more now."
Gosden senior said: "Robert committed early and made best use of her stamina.
"Eshaada came late, everyone had a go but she's very game and very honest and it was a wonderful positive ride by Robert, it really was.
"Trevor and Libby (Harris), the breeders, you go through a lot of agony as breeders but they've been fantastic for the game and they've never given up and to go and win this race is pretty special."
Eshaada runs in the colours of the late Sheikh Hamdan Al Maktoum's Shadwell Estate Company and lost little in defeat, considering her inexperience.
Racing manager Angus Gold said: "The winner went forward while we took a sit, but we were held in the final 100 yards so there are no excuses.
"It was only her third race, she will improve and technically it's all ahead of her.
"I think long term she could end up in the fillies' race back here on Champions Day."