The royal box erupted with wild cheers as the Queen’s colt raced towards the finish line.
But despite the presence of many of her grandchildren as talismans, the monarch was out of luck at the Investec Epsom Derby, as her horse, Carlton House, came in third.
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Carlton lost a shoe in the final furlong as he tried to gain ground and failed to win the race that would have rounded off an annus mirabilis for the Queen.
But her consolation prize was equally if not more rewarding – the 85-year-old was evidently proud and delighted to be surrounded by a big, happy family for the day.
Looking radiant in a pink and white ensemble, she was all smiles and clearly enjoying the company of her nearest and dearest on their first get-together since the royal wedding.
The Duchess of Cambridge was the picture of elegance in a white tweed Joseph jacket over a white chiffon Reiss dress.
She arrived on the arm of her handsome new husband Prince William, who like his brother Prince Harry, had donned a top hat and tails for the occasion.
But the 120,000-strong crowd hadn't come merely for the fashion. All eyes were on the Royal Box, which was decorated in the Queen’s racing colours of red, purple and gold in anticipation of the result.
The suspense inside was palpable. Sophie Wessex covered her eyes with her hands as Prince Harry punched the air and cheered wildly for the royal colt.
The Queen did not appear on the balcony during the race, preferring to watch it on television inside. One race official said she was "just too tense".
It was difficult to say who looked more excited between Princess Eugenie and her sister Beatrice, who was seen shouting at the top of her voice, hands balled up with tension.
Bea had dressed in a ladylike floral shift dress paired with a matching white oversized flower headpiece, further cementing her newfound sartorial clout.
Earlier in the day, Kate had been seen cheering on Sohraab, a horse in which her parents, as members of a racing syndicate, have a share.
And her mother Carole Middleton was also spotted watching the races from the stand.