As NATO leaders gathered at Buckingham Palace on Tuesday night, all eyes were inevitably on Donald Trump.
The Queen, Charles and Camilla lined up to receive the US president and his wife, but one royal appeared unwilling to join the official greeting party.
In footage from the event, Princess Anne can be seen lingering a few feet away when Her Majesty gives her a side-glance that looks to be an admonishment for not joining in.
The Princess can then be seen throwing her hands up in the air.
But according to the Press Association, Anne was standing back as she was not part of the official welcoming party, and the monarch was simply looking to see which politician was next.
Anne turned to point to the Deputy Master of the Household, Lieutenant Colonel Anthony Charles Richards, and Lord Chamberlain Earl Peel – the most senior official of the Royal Household, remarking "it's just me", before adding "and this lot".
Donald Trump arrived after earlier taking tea with Charles and Camilla.
The event was also significant for the absence of another of the Queen's children.
Prince Andrew would normally attend such engagements, but was nowhere to be seen having quit public life following allegations from Virginia Giuffre that she was forced too have sex with the Duke.
Asked earlier about the Duke, President Trump claimed he "didn't know Andrew", despite a number of photographs that appear to dispute his claim.