London tourist alert: Prince William on horseback

By the Associated Press | June 4, 2011 | 10:59 AM EDT

Prince William, the Duke of Cambridge leaves Buckingham Palace on horseback on his way to Horseguards Parade to take part in the Colonel's Review in London Saturday June 4, 2011. Every year in the months of May/June there are three Trooping the Color parades, the Colonel's Review is the second rehearsal and takes place on the Saturday one week before the Queen's Birthday Parade. (AP Photo/Stefan Rousseau/PA Wire) UNITED KINGDOM OUT

LONDON (AP) — Sharp-eyed tourists outside Buckingham Palace had a rare opportunity to see Prince William on horseback.

William was taking part Saturday in rehearsals for next week's "Trooping the Colour" ceremony to mark Queen Elizabeth II's official birthday.

The 28-year-old prince and hundreds of other soldiers practiced on a hot sunny day. He was wearing a red tunic with a blue sash from the Irish Guards as he rode a mottled gray horse called Wellesley.

The queen turned 85 in April, but tradition holds that "Trooping the Colour" — the public party for the monarch's birthday — is held in June when the weather is better. The custom dates from 1748.

William and his new wife Kate Middleton plan to visit Canada and California in late June and early July.