Her Majesty the Queen hosts the annual event, which includes a service at St George's Chapel followed by a Garter Day luncheon in the Waterloo Chamber of the Castle, and never-before-seen footage from the dining area shows just how seriously preparations are taken.
SEE the incredible work that goes into Garter Day here:
"Over the past year the huge Waterloo table has undergone a comprehensive French polish, giving it the sheen that you see today. Watch this video to see the preparation undertaken by Palace attendants & footmen the day before the luncheon."
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Royal fans were delighted with the inside look at the day, which honours the oldest and most senior order of knighthood in the UK, People Magazine reports.
One social media user wrote: "How beautiful, such hard work by the staff. Such a grand area, it must be dazzling to be there with all the people having lunch."
Another said: "Absolutely fascinating to watch!"
Prince William and Prince Charles take part in the parade
Before sitting down to lunch, Prince William and his father Prince Charles took part in the symbolic parade outside Windsor Castle, with both men donning the iconic midnight velvet robes and ornate ostrich plume hats which are the signature of the Order.
The Duke of Cambridge was made a Knight of the Order in 2008, in a ceremony attended by his then-girlfriend Kate Middleton and brother Prince Harry.
Camilla, Duchess of Cornwall, Queen Maxima of the Netherlands and Kate, Duchess of Cambridge outside St George's Chapel in Windsor
The Duchesses were joined by foreign royalty King Willem-Alexander and Queen Maxima of the Netherlands and King Felipe and Queen Letizia of Spain, as well as Prince Andrew, Prince Edward and his wife Sophie, Countess of Wessex, Princess Anne and the Queen's cousin Princess Alexandra.
King Willem-Alexander and King Felipe are honourary members of the Order.
Mother-of-three Kate - who left her little ones Prince George, 5, Princess Charlotte, 4 and one-year-old Prince Louis at home the for the day - looked radiant in the ivory 'Liza' dress by Catherine Walker and a striking black fascinator from Lock & Co.
Alice MurphyAlice Murphy is a freelance journalist and self-professed news addict. Originally from Ireland, Alice is on a mission to visit every country in the world (telling stories along the way). She is most commonly found eating sushi, drinking strong coffee and reading horoscopes.