The Duke of Cambridge took a brief break from parental duties following the birth of his son, Prince George, as he played in a charity polo match.
Prince William joked that it was "good to get out of the house" - but said he had to buy some nappies for his son, born on 22 July, on his way home.
He also added: "I've got to make sure I'm not too late back!"
The prince said his son "likes to move around a lot, he wriggles a lot, he keeps us on our toes".
He scored the winning goal in the match, which was his first public appearance since Prince George was born.
Prince William was presented with a child's polo mallet after the match and joked: ''Is it nappies?''
The match, in which his brother Prince Harry also played, was the 11th annual challenge game in support of charities SkillForce and the Royal Marsden Cancer Charity, of which Prince William is patron and president respectively.
The duke is currently on paternity leave from his job as an RAF search and rescue pilot.
Meanwhile, Prince Charles received presents and cards for his grandson from well wishers as he attended the Mey Games - the world's smallest Highland games competition - in Caithness.