Raffle Prize asserted late on to take the Group 2 Duchess Of Cambridge Stakes in style under Frankie Dettori.
The Mark Johnston-trained filly was always in contention, travelling well up the rail before cruising clear of favourite Daahyeh in second to win by a length and three-quarters, with Final Song taking third.
Victory for Raffle Prize follows a rousing success in the Queen Mary at Royal Ascot, and got Dettori off to the best possible start on day two of the July meeting.
Raffle Prize winning the Queen Mary, photo Liesl King
Following the race, the superstar jockey said: "She's very smart and has improved since Ascot. She was giving weight to all the runners today and I thought it was an amazing performance."
The two big successes have prompted discussion over the daughter of Slade Power's potential to run in next year's Qipco 1,000 Guineas and Commonwealth Cup, for which she has been priced up at 14-1 with Paddy Power.
Dettori added: "It's a long way to go until next year, but she has lots of scope. She's a big filly so I'm sure she'll train on."