Aidan O'Brien's Was claimed victory in the Investec Oaks at Epsom in the hands of Seamie Heffernan.
The 20-1 chance was ridden positively in the early stages of the mile-and-a-half contest, just tracking the early pace set by Nayarra, with stablemate Twirl also well to the fore.
Leading fancy Vow ranged up to make a race of it at the top of the home straight, but Was quickened best of all against the far rail to take top honours by a neck. Shirocco Star ran a stormer to finish second, with 11-4 favourite The Fugue coming from a long way back to claim third and Vow fourth.
Even with Kissed having been withdrawn earlier in the day, Was featured among five O'Brien-trained fillies in the race, with 1000 Guineas third Maybe the most fancied.
Was won her only juvenile appearance at the Curragh last August, but was beaten into third in last month's Blue Wind Stakes at Naas.
In a race where it proved sensible to be prominent off a slow gallop, the three-year-old showed plenty of dash to claim a surprise victory.
Shirocco Star's run was particularly meritorious given she was fractious in the preliminaries.
The Fugue and William Buick were short of room in the early stages and ended up further back than ideal, but she finished off her race well and arguably goes down as an unlucky loser.
Vow travelled like the winner for a long way and ran a creditable race in fourth.
Maybe was another filly who was a long way back for much of the journey in the hands of the trainer's son, Joseph, before staying on for fifth.
Afterwards, the winning jockey said: "I had enough horse to take two lengths when I needed it.
"I've been very lucky in these colours and I have the owners to thank for trusting me.
"I was on the bridle and had plenty of petrol. When you have plenty of petrol you can go where you like."
O'Brien was securing his fourth Oaks success, with his last victory in the Epsom Classic arriving with Alexandrova in 2006.
The master of Ballydoyle was also preserving his unbeaten record in British Classics this term after Camelot and Homecoming Queen struck in the 2000 and 1000 Guineas respectively.
O'Brien said: "Seamus gave her a lovely ride, she came on lovely from her first run so we were delighted.
"She's a very good looking filly with a great pedigree. He's a great fellow, Seamus, a world-class jockey. He knows all these horses inside out and and nobody deserves it more."
