Her Majesty, 96, has chosen to watch the races on television at Windsor Castle in Berkshire as she continues to experience ongoing mobility issues.
Racegoers had hoped the monarch would make an appearance, with her home just a 15-minute drive away.
The Queen had more than 10 horses entered over the five day event. It is believed has been kept abreast of developments by her racing advisor John Warren.
The Queen's horse Reach For The Moon was a favourite with some bookies to win the Hampton Court Stakes on Thursday with jockey Frankie Dettori taking the reins.
However, the colt was well beaten into second place by winner Claymore, which led from the start and pulled away from Dettori.
The Prince of Wales and Duchess of Cornwall led the royal party on the event's first day on Tuesday, taking part in the traditional carriage procession along the course before the racing began.
They were followed by the Princess Royal and minor members of the royal family, including the Duke and Duchess of Gloucester and Prince and Princess Michael of Kent.
Princess Beatrice and her husband, Edoardo Mapelli Mozzi, walked through the gates to the course with other punters and were surrounded by photographers before making their way into an exclusive area.
Royal Ascot is as much a social occasion as a sporting event and female racegoers wore summer dresses and flamboyant hats while the men sported top hats and tails or smart suits.
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