The Queen looked ecstatic on the third day of Royal Ascot today as her horse Estimate romped home to win the meet's prestigious Gold Cup. But, perhaps, not quite as thrilled as her jubilant granddaughter Princess Beatrice. The dark bay thoroughbred filly was the 7/2 favourite and won by a length - much to the monarch's delight, who became the first reigning monarch ever to win the trophy. As Princesses Beatrice and Eugenie jumped up and down in excitement in the royal box, the Queen clapped her hands as the horse crossed the finish line first and beamed at her racing manager, John Warren, who was sitting beside her. Estimate's achievement made sporting history as the Queen became the first reigning monarch to win the Gold Cup in its 207-year history. The Queen was hoping Estimate would surpass her achievement of last year when she won the Queen's Vase at Royal Ascot. The horse lived up to her billing as favourite and as the Gold Cup, raced over 4,000 metres, drew to a close, she made her way from the middle of the pack, took on the front runners and beat them to the line. The victory is an added boost for the Queen who has been attending the famous race meeting without the Duke of Edinburgh, who is convalescing at Windsor Castle after exploratory abdominal surgery. Her grandson Peter Phillips said: 'It's amazing, this is her passion, every year she strives to have winners and to have the big one at Royal Ascot means so much to her and to everyone involved in racing. A win like this is truly, truly special.' After revealing that the Queen had been congratulated by fellow monarch and racehorse enthusiast, Sheikh Mohammed bin Rashid Al Maktoum of Dubai, he added: 'Everyone is just thrilled... to see a result like this is just brilliant.'