The King received words of support from actor Sir Idris Elba who sympathised with Charles being drenched by rain.
Charles chatted briefly to the Luther star when the two men met unexpectedly at a popular historical tourist attraction in Antigua as they attended separate events.
The King is in the Caribbean country to deliver the keynote address opening the Commonwealth Heads of Government Meeting (CHOGM) on Tuesday, expected to be dominated by the issue of a slavery apology and reparations.
Charles attended celebrations marking the 45th anniversary of Antigua’s independence from Britain on Sunday, but got caught in a torrential downpour moments after he arrived with Camilla at a cricket stadium hosting events.
He was seen throwing his arms up and calling repeatedly for an umbrella from members of his entourage, but later saw the funny side saying “I’ve started growing watercress on my trousers”.
Charles was visiting Nelson’s Dock and had just set an engraved stone into a wall when he was reunited with Sir Idris, a goodwill ambassador for the King’s Trust, who was hosting the One Commonwealth Night concert at the Unesco World Heritage Site.
“How are you?” the actor and knife crime campaigner said as he shook hands with Charles and they greeted each other like old friends.
The King asked “What are you doing here?” and both laughing Sir Idris replied “I get around”, affectionately patting the King on the arm.
Sir Idris said: “How are you doing though, are you having a good time?” and then sympathised with Charles getting caught in the rain.
It had been thought the actor made a comment about the Prime Minister of Antigua but his words were later clarified.
Sir Idris, who first found fame with the acclaimed US series The Wire, got his acting start thanks to a grant from Charles’ Prince’s Trust that helped him attend the National Youth Music Theatre.
The 54-year-old celebrity, who is best known for his role as DCI John Luther in the BBC crime series, was knighted earlier this year for services to young people.
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