Nato leaders appeared to mock Donald Trump at a Buckingham Palace reception.
A huddle which included Prime Minister Boris Johnson and the Princess Royal was filmed apparently gossiping about the US president's unorthodox style on Tuesday night, although Trump is not mentioned by name.
During the casual chat, as the leaders sipped drinks, Johnson can be heard asking French President Emmanuel Macron: "Is that why you were late?"
Canadian Prime Minister Justin Trudeau says: "He was late because he takes a 40-minute press conference off the top."
Later in the conversation Trudeau adds: "You just watched his team's jaws drop to the floor."
A video clip of the chat, filmed as world leaders met ahead of a summit to mark Nato 's 70th anniversary, has been viewed almost four million times since it was posted online.
It came after Trump branded Macron's comments that Nato is "brain dead" as "very nasty", before the pair met on Tuesday at the US ambassador's residence in London.
Trump also pressed Trudeau on Canada's Nato spending at their bilateral meeting.
Meanwhile, following an evening reception hosted by Johnson at Number 10, a member of the US Secret Service was pictured leaving with a Christmas bauble gifted to leaders.
Each Nato leader was given one of the decorations and invited to hang it from the Downing Street tree.
