Britain's Queen Elizabeth had special cause for celebrations on Thursday when her horse Estimate won the Royal Ascot Gold Cup. _0"> On a day of sentimental successes and broken records, it was the first time a reigning monarch's horse had claimed victory in the race's 207-year history. Estimate, a four-year-old filly trained by Michael Stoute, held off a challenge by Simenon in the final furlong to win by a neck and initiate a rapturous reception for the Queen in the winner's enclosure. The Queen was expected to present the winner's trophy, but instead received it from her second son, the Duke of York. Estimate, a 7-2 favorite, won at Royal Ascot last year when landing the Queen's Vase. The Queen's grandson Peter Phillips told Channel 4: "It's amazing! This is her passion and her life. "She's here every year and she strives to have winners -- to win the big one at Royal Ascot means so much to her." Jockey Ryan Moore