Royal Kate Catherine Kaye MIddleton uniform regal ceremony emblem
Royal Kate Catherine Kaye MIddleton uniform regal ceremony emblem

The royals certainly are mad hatters!

Kate Middleton, Prince Charles and other members of the British Royal Family joined Queen Elizabeth at Windsor Castle for the annual Order of the Garter ceremony on Monday -- and in true British form they were some funny hats on their heads!

For the ceremony, the Duchess of Cambridge wore a powder blue Christopher Kane coat dress and a Lock & Co. fascinator (that's British talk for fancy lady hats).

The Order of the Garter was founded by Edward III in 1348 and is the oldest British order of chivalry. At the event, more than 7,000 spectators watched the Garter Knights process through the castle grounds to St. George's Chapel.

The Order of the Garter event takes place every June on the Monday of Royal Ascot week, also known as Garter Day. During the event, the knights wear blue velvet robes and black velvet hats with white plumes.