LONDON -- Prince William was made a Royal Knight of the Garter on Monday at a ceremony presided over by his grandmother— the British monarch—and attended by his father, brother and girlfriend.

Queen Elizabeth II made William the 1,000^th knight to join the order and formally presented him with the regalia, including a blue garter, sash and star brooch.

After the ceremony at Windsor Castle, the knights wore their traditional ostrich feather hats and velvet robes as they walked to St. George’s chapel in the castle grounds for a service.

William’s girlfriend Kate Middleton, dressed in a black suit and hat, watched the procession with his brother Prince Harry.

The Order of the Garter was established in 1348; the monarch can give the honor to anyone she chooses without advice from government ministers. It is meant to honor those who have held public office, who have contributed to national life or who have served the queen personally. William, 25, is second in line to the throne after his father, Prince Charles.

Two former prime ministers, Margaret Thatcher and John Major, are members of the order.

The garter itself is a dark blue velvet strap with the words “Honi soit qui mal y pense, old French for “shame upon him who thinks evil upon it.”