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.

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