John Gosden won his third Nassau Stakes in as many years as Sultanina denied Narniyn at Glorious Goodwood on Saturday.
The four-year-old filly was dropping back in trip following a good second in the Lancashire Oaks last time but her proven stamina was put to good use in the Group One contest.
Held up by William Buick in the early stages as Venus De Milo took them along, the daughter of New Approach mounted her challenge down the outside as Narniyn took over from Aidan O'Brien's filly.
It took her a while to get on top, but once she hit the front there was no stopping her, and she was driven out for a length-and-a-half success.Buick said: "I'm absolutely delighted for everyone - it's fantastic.
"This filly has really stepped up to the plate.
"It was only the fourth run of her life so it was a good training performance.
"We've always held her in high regard, but no-one as high as her owner."
The Nassau is a race Gosden has dominated recently with The Fugue in 2012 and Winsili last year.
Gosden said: "It's lovely. The Aga Khan's filly (Narniyn) is a really good filly to come over and is a tough nut to break.
"The last furlong and a half was a right duel between the pair.
"This filly is very classy and Philippa (Cooper, of owners-breeders Normandie Stud) bred her down the road, just 11 miles from here, and she always told me this filly was the best and I could never work it out.
"I didn't run her until this year as a four-year-old. She's gone and won a maiden, a Group Three, second in a Group Two and now won a Group One, so it's unbelievable.
"We're going to enter her on Tuesday in the fillies' and mares' race on Qipco Champions Day in October.
"I might just freshen her for that and go straight there and bring a fresh filly for the autumn."
Trainer Alain de Royer-Dupre said of the runner-up: "I think the ground was too fast for her, she was changing her legs.
"She did well but she has the capacity to do better.
"Her next race will be the Prix Jean Romanet at Deauville in three weeks."
Venus De Milo is now likely to head to York later this month.
Trainer Aidan O'Brien said: "It was a solid run but she'd prefer going further and she was a little bit at sea on the track as well.
"She wants to be racing so I'd say she will go for the Yorkshire Oaks.
"York will suit her better."