LONDON (AP) — Queen Elizabeth II is marking her official birthday with the annual Trooping the Colour parade, a traditional display of British pageantry.

About 1,400 soldiers in ceremonial scarlet coats and bearskin hats march past the queen in a ceremony on Horse Guards Parade in Westminster.

Royals taking part included Prince Charles, Prince William and his wife Kate, and Prince Harry and his wife Meghan.

Thousands of spectators have lined the parade ground and gathered in nearby St. James’s park to watch the spectacle.

The ceremony originated from traditional preparations for battle. The colours — or flags — were “trooped,” or carried down the lines of soldiers, so they could be seen and recognised in battle. The regimental flag being paraded this year is from the 1st Battalion Grenadier Guards.