He returns to his search and rescue job with the Royal Air Force.
Over the weekend, William made his first public appearance since the July 22 birth of Prince George.
He m gave guests at a charity polo match an insight into his newfound paternal duties, saying his mind had been stuck in "baby mode" thanks to his feisty newborn son.
William was playing alongside his brother Harry at the Audi Polo Challenge in the English village of Ascot. The match came less than two weeks after he and his wife, Kate, had their first child, Prince George, and William told spectators it was "good to get out of the house" for the afternoon.
The 31-year-old royal managed to score the winning goal for his team and was later presented with a miniature polo stick for his baby boy. He jokingly asked if he'd be getting some nappies - the British term for diapers - instead, telling guests he had to "pick some up on my way home."
Of his performance on the pitch, William said he was "in baby mode out there, thinking about nappies. I wasn't really in the zone." When quizzed about George, he said the little prince, who was born July 22, "likes to move around a lot. He wriggles a lot. He keeps on our toes."
The polo outing was William's first public appearance since the birth of his son captured the world's attention. Kate and the baby were not in attendance.
(The Associated Press contributed to this report)