It was the future king’s 15th appearance at the Guards Polo Club event.
The Princess of Wales cheered from the sidelines as William competed on a baking hot polo pitch in a charity cup.
The Prince of Wales rode alongside top professional players as well as keen amateurs at the Guards Polo Club, near Windsor, on Friday, with the day’s sport set to push the Royal Charity Polo Cup’s fundraising total to more than £15 million.
Kate wore a gingham dress and sunglasses as she debriefed with her sportsman husband partway through one of the games, with Windsor Castle peering above in the far horizon.
It was the future king’s 15th appearance at the event and William, as usual, played the defensive position of number four.
Commentator Karl Ude Martinez reminded the crowd of the royal family’s polo legacy and how William and the Duke of Sussex used to compete together.
He said: “Obviously his brother plays, they play a lot together – they used to play a lot together.
“His father played, King Charles got up to a very good handicap – their grandfather played, the late Duke of Edinburgh, Prince Philip, he played for many, many years and competed in many a big tournament.
“Their father before that played. They’ve played for many, many generations and it is something that is very close to their heart.”
Mr Martinez praised William’s defensive skills that led his US Polo Association team onto a goal as temperatures neared 30C.
Polo players must hold the mallet in their right hand and the commentator said: “In fact, the Prince of Wales is left-handed but he had to learn to play with his right hand – he’s also an Aston Villa fan but we won’t hold that against him.”
William braved the heat as “a true professional”, Mr Martinez said, adding: “He has played for many years but he doesn’t often get time to play.
“He doesn’t get time to play at all, really, because of his commitments and his busy schedule.
“To have him here today to play is truly a very, very rare occasion.”
William’s squad included former England captain Mark Tomlinson, Saudi businessman Amr Zedan and Leicester City FC chairman Aiyawatt Srivaddhanaprabha.
Guests started the day with a champagne reception before a silent charity auction for causes including Wales Air Ambulance, the Royal College of Paramedics, mental health service Shout which aids those in crisis via text messaging, and the Maternal Mental Health Alliance.
