The Queen and Prince Philip have taken their seats in St George’s Chapel alongside Eugenie’s mother, the Duchess of York, and her sister Beatrice.
Among the 850 guests are the Dukes and Duchesses of Cambridge and Sussex, and stars Demi Moore and Liv Tyler.
Princess Eugenie is ninth in line to the throne and granddaughter of the Queen.
Another 1,200 members of the public selected by ballot will listen to a live broadcast in the castle grounds, and thousands are watching outside in extremely windy conditions.
Princess Eugenie is the Queen’s granddaughter and is ninth in line to the throne
The ceremony is being held at 11:00 BST in St George’s Chapel at Windsor Castle
Prince George will be a page boy, and Princess Charlotte will be a bridesmaid
Princess Eugenie’s fiance, Jack Brooksbank, proposed in January this year
The couple invited 1,200 members of the public to watch the wedding
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