Prince William was the surprise guest at the annual Highland games gathering in the Scottish village of Braemar.
He joined his grandparents, the Queen and the Duke Of Edinburgh, plus 17,000 other spectators at the event.
The Royal party watched competitors take part in sports including tossing the caber and tug-o-war.
The games date back to 1832 and the Royal family have been regular visitors since Queen Victoria first went to the event in 1848.
One of the Queen's residences - Balmoral - is near to the event ground in Aberdeenshire.
The prince, wearing a blue suit, chatted to his grandparents as they watched the games.
A games spokesman said: "It was a lovely day and it was a really nice surprise to see Prince William because we didn't know he was coming."