The monarch clapped her hands with delight as the four-year-old crossed the line, while Princesses Beatrice and Eugenie jumped up and down with excitement next to her in the royal box.
The Queen had been due to present the trophy to the winner of one of flat racing's most famous races, but instead her son the Duke of York had to step in to hand the cup to her.
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The win is the Queen's biggest since 1977, when her horse Dunfermline won The Oaks and the St Leger, two of flat racing's five classics.
It will have been tempered only by the absence of the Duke of Edinburgh, who was watching on TV at Windsor Castle where he is recovering from abdominal surgery.
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