Britain's royals all decked out for Order of the Garter ceremony

A day after stepping out in casual clothes at a Father's Day polo match (with Prince George in tow), Prince William and Kate were among the British royals all dressed up for the traditional Order of the Garter ceremony.

Queen Elizabeth II, Prince Philip, Prince Charles and William took part in the annual procession and service at Windsor Castle on Monday, wearing ornate blue velvet caps and hats with plumes.

Kate, wearing a pale blue Christopher Kane coat and Lock & Co. hat, watched the procession with Sophie, Countess of Wessex (Camilla, Duchess of Cornwall, missed the event after developing sinusitis, according to BBC News).

As William, 31, arrived alongside his father, he looked over at his wife and she was seen beaming back at him. Later, Kate, 32, joined her husband and father-in-law in an open-topped carriage, waving at onlookers as they rode back to the castle.

The Order of the Garter is the oldest British order of chivalry, founded by Edward III in 1348. Membership in the order is limited to the sovereign, the Prince of Wales and no more than 24 members.

Monday's ceremony came after a busy weekend for the royals. They also took part in the official public celebrations of the queen's birthday -- known as Trooping the Colour -- on Saturday, and William and Harry played in that charity polo match on Sunday, as Kate and little George watched.