A huge ceremony takes place every year at Windsor Castle that dates back to 1348. New knights take an oath and are invested with the insignia of the Order of Garter. The Queen and the knights wear blue velvet robes, black velvet hats and white plumes (feathers).
A limited number of tickets is available for members of the public to stand inside the precincts of Windsor Castle and watch the procession to St. George's Chapel. Apply between 1 Jan and 1 March by sending an email to Garter day email@example.com.
For more information please see this link.