London CNN  — 

Justin Trudeau’s gossipy conversation with several world leaders about US President Donald Trump wasn’t the only viral moment to come out of NATO’s two-day summit in London. At a Buckingham Palace reception, Britain’s Princess Anne was seen shrugging at Queen Elizabeth II – a gesture that was widely misinterpreted.

In video filmed Tuesday evening at the palace, the Queen – joined by Prince Charles and Camilla, the Duchess of Cornwall – is seen shaking hands with Trump and his wife Melania.

The 93-year-old monarch then looks across the room, apparently to check which world leader she is due to receive next, before noticing her daughter standing in the background by the door.

Queen Elizabeth says something inaudible towards Anne, who can be heard replying: “It’s just me,” before adding: “and this lot,” gesturing towards members of the royal household behind her. The group around the Queen giggles.

Princess Anne speaking to German Chancellor Angela Merkel at Buckingham Palace on Tuesday night.

It wasn’t long before “Princess Anne” was the top trend on Twitter on Tuesday. Some social media users suggested that the Queen was “scolding” Anne for not greeting the president. But according to the PA Media news agency, Anne was standing to one side because she did not form part of the official welcoming party.

The Queen was apparently looking up to see who was due to be greeted next, PA reported, and Anne’s joke referred to the fact that Trump was the last of the NATO leaders to be presented to the monarch.

Princess Anne was also caught on camera later at the same event, alongside world leaders who were appearing to joke about Trump.

That video appeared to show British Prime Minister Boris Johnson, French President Emmanuel Macron, Canadian Prime Minister Justin Trudeau, Dutch Prime Minister Mark Rutte and the princess laughing about the US President’s behavior during the summit.

The 25-second clip, which was first reported by CBC, begins with Johnson asking Macron why he was late. Trudeau can be heard replying: “He was late because he takes a… 40-minute press conference at the top.”

When Trump was asked about the exchange later, he called Trudeau “two-faced,” before adding, “honestly with Trudeau, he’s a nice guy.”

Microphones could only pick up snippets of the conversation at the reception, to which the press was given limited access. None of the leaders seemed to be aware that the conversation was being recorded. They were, however, talking openly and loudly enough to be heard by others.

Trudeau admitted Wednesday that the group had been talking about the US President. “Last night I made reference to the fact that there was an unscheduled press conference before my meeting with President Trump. I was happy to be part of it but it was certainly notable,” Trudeau said during a Wednesday press conference.

Correction: The headline on this story has been corrected to better reflect the circumstances of the Queen's gesture.