Britain's King Charles joked that he and Elton John were "still standing" in a clip recorded for the singer's radio show which was aired on Saturday - the monarch's 78th birthday.
Charles had joined John for a special edition of the singer's "Elton John's Rocket Hour" on Apple Music to celebrate 50 years of The King's Trust and musicians who have supported his youth charity.
During the episode, which was first broadcast on Saturday to coincide with the king's birthday, the pair discussed benefit concerts held in support of the Trust including a Rock Gala held at Wembley Arena in 1986 where John performed his hit I'm Still Standing.
"I know people in all kinds of circumstances find this song inspiring, not only for its marvellous spirit, but also its message of resilience," Charles said. "And certainly 40 years on from that remarkable concert, we and the Trust are definitely still standing."
John, who is 79, replied, "I'm still sitting now, though", prompting laughs from the king.
"With occasional bits dropping off here and there," Charles said. "I know this is a terrible problem as we get older."
Both men have suffered well-documented health problems in recent years, with the king still undergoing treatment for cancer and John suffering problems with his eyesight.
When he was the heir, Charles founded the Prince's Trust in 1976 using his Royal Navy severance pay to help disadvantaged young people prepare for work, find jobs or start businesses.
It was renamed the King's Trust after Charles became king in 2022 and the charity says it has supported more than 1 million young people since its launch.
John's Rocket Hour is a weekly show that has aired globally on Apple Music 1 since 2015.
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