Prince William and Kate Middleton
Pictured: Prince William and Middleton attend the Coach Core graduation ceremony for more than 150 Coach Core apprentices at The London Stadium on Oct. 18, 2017 in London. Getty Images/Chris Jackson

Part of being a royal means being a master at etiquette. Kate Middleton and Prince William have this down pat but there was a moment where everything they've learned was tested.

That moment can be traced back to their 2016 royal tour when the Duke and Duchess of Cambridge made a stop in Canada. Royal commentator Emily Andrews gave all the details when she appeared in the "Secrets Of The Royals" documentary.

"When I was on tour with William and Kate in 2016 in Canada, we were at this lovely presentation of seasonal Canadian produce. Sun was shining, Kate was looking gorgeous, I was like 'oh this is lovely'," she began, according to Express. "And suddenly we see this clam called geoduck."

"It’s a very phallic-looking, kind of long tube and kind of a bulbous part at the end. It’s a delicacy and you eat it. And bless them, they both tried it," Andrews continued.

She added, "They managed to stifle any kind of giggles. I think they had it chopped up, they didn’t have to put the whole thing in their mouth, which would have been pretty gross."

The British publication also reported that Etiquette and Civility Specialist, William Hanson chimed in during the documentary and noted that Kate and Will's actions are similar to what Queen Elizabeth had done "because she’s very dutiful and she doesn’t want to offend her hosts."

Being that Prince William and Kate will be the future King and Queen of England it's no surprise that they remained respectful and open-minded while on their royal tour. The parents of Prince George, Princess Charlotte and Prince Louis, aren't always ones to be strictly by the book though. The royal couple has broken royal protocol before and even have plans to do so in the future with their 2019 royal tour.