Sultanina (10/1) led home a one-two for John Gosden in the Group Three Pinnacle Stakes at Haydock Park.
There was a thrilling finish to the 12 furlong contest for fillies and mares with the first three home separated by less than a length.
Frankie Dettori on Freedom's Light was the first to strike for home after Cubanita looked like she had moved into it nicely, as Astonishing and Special Meaning weakened out of it having cut out the running.
It appeared for much of the final furlong as though Dettori was going to land the prize only for William Buick to persude his once-raced Salisbury maiden winner to put her head in front where it mattered.
A short-head separated the pair with Silk Sari a further half-length away having finished strongly on the step up from handicap company.
Buick said: "Me and Frankie had it in front from two and a half out, and there's no-one worse to be alongside in a situation like that.
"I knew it was close, but I would have been disappointed if she got beat as she's still very green and she's quite talented.
"The owner Mrs Cooper said she thinks a lot of her and she was definitely right. It was a hard choice (which to ride), there was nothing in it as you can see."
Normandie Stud owner Philippa Cooper said: "I can't believe it. I didn't think she'd won. When they called number 11 I nearly threw up!
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"We waited a long time for her to run as she had trouble with sore shins, but my trainer (Gosden) obviously had a lot of faith in her as he wouldn't normally keep a horse in training as a four-year-old if they had never run before.
"She won her maiden at Salisbury a couple of weeks ago and we pitched her in at the deep end today. Just to finish in the first four would have been fantastic.
"She's so tough and winning races like this is what it's all about. This means so much, I haven't even thought about where she'll go next."