Brave Anna got up late under Seamie Heffernan to claim the opening Albany Stakes on day four of Royal Ascot.
The Aidan O'Brien trained filly took the Group Three honours from Ralph Beckett's Bletchley after a photo finish.
O'Brien also supplied the 2-1 favourite for the race in Cuff but the Ryan Moore-ridden filly could not quicken in the final furlong.
Having missed the break Heffernan's 16/1 shot had plenty of ground to make up on the likes of Create A Dream and Sea Of Snow, but the daughter of War Front knuckled down well.
She had to live up to her name close home, as Bletchley and Richard Fahey's Frankel filly Queen Kindly made her pull out all the stops.
The 16-1 winner crossed the line just a short head in front of Bletchley, with half a length back to Queen Kindly.
It was a third Royal Ascot winner for Heffernan, who is a crucial part of the Ballydoyle operation.
The winner is a full-sister to the same owner's Breeders' Cup winner Hit It A Bomb.
Heffernan said: "She's a lovely filly and came here on the back of a good win at the Curragh. It's nice we can pitch up here on the big day and win again.
"Aidan told me to give her a chance and hopefully she'd finish out well and that's what she's done."
O'Brien said: "She works like a good filly, but I thought she'd improve going up to seven furlongs and we nearly left her at home.
"Mrs Stockwell (owner) said 'let her take her chance' and that's why we're here.
"She is brave, but she'll be better when stepped up to seven furlongs and Seamie gave her a fantastic ride.
"She did the same at the Curragh - she was the second string there and defeated a more fancied runner of ours (How).
"A mile should be no problem. She could be a Guineas filly, as she's a big filly who is developing all the time."
Ballydoyle maestro O'Brien made it a big-priced double as Sword Fighter and Colm O'Donoghue made all the running to win the Queen's Vase at a whopping 33-1.
It was O'Brien's fifth win in the race since 2007.
Laura Mongan's Harbour Law who threw down the biggest challenge but he failed by three-quarters of a length.
Jim Bolger's Twilight Payment flew from the rear to claim third at 20-1.
O'Brien said: "Colm gave him a class ride. He dictated the pace lovely the whole way and got it absolutely spot on.
Across The Stars then bounced back from a disappointing run in the Derby to win the King Edward VII Stakes, taking Sir Michael Stoute within one win of the late great Sir Henry Cecil's Royal Ascot record of 75.
Having finished only 10th at Epsom behind Harzand, he perhaps did not have as hard a race as some there as once his chance had gone he was allowed to coast home.
Frankie Dettori was booked by Sir Michael Stoute for the colt and had him in the perfect position, just behind Moore who tried to make all on Beacon Rock.
Across The Stars was keen enough in the early stages, but Dettori, riding full of confidence, has few peers in getting them to settle.
His mount had to be brave to get through a narrow gap between Beacon Rock and Choreographer and while he took a narrow lead, Beacon Rock would not give in lightly.
Stoute, who has an excellent record in the race, will have liked the way his charge stuck to his task and the 7-1 winner kept the Ballydoyle runner at bay by a length and a quarter.
John Gosden's Muntahaa made eyecatching late gains from the rear to claim third.
Dettori said: "To win the 'Ascot Derby' is great. (Sir) Michael has been hitting the crossbar and I'm pleased to get him a winner.
"He's a master trainer and he had this horse well prepared for today.
"He didn't come down the hill at Epsom, (but) he handled this track really well and we won."
