The couple enjoy the sport so much so they can't help but get invested in the match as they sit and atch the match unfold in the royal box, although the Duke of Cambridge got a little too caught up in the moment during the men's Quarter Final on Tuesday.
While watching the heats unfold the 40-year-old royal appeared to have a slip of the tongue and swore.
Prince George, Louis and Princess Charlotte's dad could be seen mouthing the words "No, no, no f*** it" on camera.
And it is no surprise swearing in public is a total faux pas for members of the royal family, as it breaks the royal protocol if they do.
The camera swiftly panned away from William, so you can't be sure exactly what he said, although you can make out the beginning of the word.
The moment did not go unnoticed by eagle eyed fans, who took to social media to share their views on William's cursing.
One tweeted: "The Duke of Cambridge has his moment like the rest of us a slip of the tongue."
Another shared: "Bit of a character, just like his grandfather."
A third wrote: "Can't be unseen! So glad he's human."
While other fans were quick to jump to William's defence, as one wrote: "He was about to say ‘for goodness sake’ when the camera cut away."
Another reacted: "I think Prince William was complaining about being too hot so was loosening his tie."
William isn't the only royal who has been caught out misbehaving, as his children have been spotted hilariously pulling faces in the past while at royal engagements.
Cast your mind back to the Trooping the Colour celebrations over the years, which has seen Princess Charlotte poke her tongue out behind the curtain, Prince George pull funny faces on the balcony, Prince Louis cover his ears to shield from the noise of the flypast, and Savannah Phillips covering George's mouth to stop him singing - plus plenty more funny moments.
Meanwhile, the royal family have been advised to take a 'step back' to evaluate their royal tour actions, as there is growing speculation the Cambridge's will be embarking on a royal tour in the coming months.
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Maisie is a writer and editor, covering Royal News, Showbiz, Lifestyle content, as well as Shopping Writing and E-Commerce, for print and digital publications, including Marie Claire, Hello!, Fabulous, Mail Online and Yahoo!.
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