This is the moment the Princess of Wales couldn't help but break her composure in the middle of a formal event.
Catherine, 44, was seen listening intently to King Charles's speech at a state banquet for the Sultan of Oman on the evening of 20 October.
But she couldn't help but break into a smile when the King mentioned her husband, Prince William, who was sitting opposite her.
Catherine had been seen with a neutral expression, as was appropriate for the formality of the occasion.
© Getty ImagesBut she couldn't resist proudly beaming at her husband through a gold ornament on the table, showing her delight that he'd received a special shoutout.
You can watch the heartwarming moment in the video above – did you spot it?
King Charles mentions son Prince William in his speech
The King spoke proudly about William as he hosted Sultan Haitham bin Tarik al Said at the start of his state visit last week – and this is what prompted Kate's special smile.
Charles said there can be "few happier symbols of success" than watching a relationship passed between generations – a reference to the Prince of Wales and Sayyid Theyazin, who were joint patrons of an Omani expedition.
The King told the Sultan: "Our connections matter deeply and, in this regard, I have been especially delighted to see our sons, the Prince of Wales and His Highness Sayyid Theyazin, become joint patrons of the Jewel of Arabia Expedition."
© GettyThe two royal heirs were the figureheads of the expedition, a 30-day journey on foot, by camel and by 4×4 staged last year through Oman, following the route of British explorer Bertram Thomas in 1928.
Charles added: "Your Majesty, there can be few happier symbols of success than a living relationship being passed from one generation to the next."
His speech came just hours after the publication of Prince Harry's interview with GQ Magazine, where he insisted he wants to "work it out" with his family, but that others "don't want to".
A spokesperson for the Duke later insisted that the comments were not intended as a "swipe" at his brother.
Catherine and William's important role during state visit
The Prince and Princess of Wales are taking on more responsibility during state visits in preparation for one day becoming King and Queen.
For example, during last week's visit, William greeted the Sultan at his London residence on behalf of the King.
However, he was not joined by Catherine, as the Sultan's wife had not accompanied him on the visit.
He reunited with Catherine on the royal dais at Windsor, before the formal carriage procession and the viewing of items in the Royal Collection.
The couple is currently spending time away from the public eye as it's half-term for their three children, Prince George, 13, Princess Charlotte, 11, and Prince Louis, eight.
During a visit to The Treehouse Hospice and cafe in East Anglia last week, the Princess admitted she had "missed" her eldest son George while he's been away boarding at Eton College.
