Former Samoan professional rugby player Freddie Tuilagi, 53, held out a hand towards Charles and asked him for a dance at the King’s Commonwealth reception.
Pausing momentarily to offload his drink, the King beamed as he held his arms out and copied Tuilagi’s fluttering hand gestures.
At one point Tuilagi, an honorary consul with the Samoan High Commission, gave the King a ceremonial fly swat (a fue), which was hung over his shoulder.
Tuilagi said after the performance: “I told King I’m going to dance for you, when you go to Samoa, this is how they will dance.”
Asked to critique the King’s performance, he replied: “Good, he’s got the moves.”
Charles, 75, was joined by Queen Camilla, Sophie the Duchess of Edinburgh and the Duke of Kent at a reception ahead of the Commonwealth Heads of Government Meeting (CHOGM) in Samoa.
The King and Queen will both be in Samoa for CHOGM later this month.
Among the 375 guests at the palace were Jamaican-born singer Grace Jones, 76, South African Strictly Come Dancing judge Motse Mabuse, 43, and Aussie judge Craig Revell Horwood, 59.
Foreign Secretary David Lammy was also in attendance.
Grace Jones said: “I have met them a few times, ever since James Bond.
“I also did the hula hoop for the Queen at the Jubilee. So we have a history.
“Being Jamaican I believe that the Commonwealth has positives. It’s a very good thing that brings people together in a positive way.”
England rugby player Joe Cokanasiga gave the King a traditional greeting, kneeling and clapping three times.
He said afterwards: “I am originally from Fiji and it’s a sign of respect to the heads of state.
“I have been practising that. He definitely knew I was from Fiji after I did it as he experienced it before.
“The Commonwealth is important and I wouldn’t have been here because my dad joined the army he moved here. It gives people a lot of opportunities.”
Also present were Commonwealth High Commissioners and representatives and supporters of The King’s Trust International and the British Asian Trust, The Wow Foundation and The Queen’s Reading Room.