Dominic Lipinski/APWho's that lad? Prince William dons traditional tall bearskin hat and rides horseback.
The prince was on horseback and riding in plain sight, but he was wearing a traditional tall bearskin hat that mostly obscured his face.
William, 28, was rehearsing for his role in next week's birthday celebration for Queen Elizabeth.
The queen actually turned 85 in April, but the hoopla - dubbed "Trooping the Color" - is held in June when the English weather improves. The party is expected to draw thousands of visitors into central London.
The couple also made an appearance Saturday at the Epsom Derby, a prestigious horse race held outside London.
The famed couple will be traveling to the United States next month as part of its first overseas trip as a married couple. They will be spending three days in Los Angeles after a week touring several Canadian cities.
Meanwhile, Kate Middleton's sister Pippa, whose good looks nearly stole the show at the royal wedding, spent Saturday running in a triathlon.