Catherine, Duchess of Cambridge shakes hands with Jon Hamm as she attends the Royal Film Performance and UK Premiere of “Top Gun: Maverick” at Leicester Square on May 19, 2022 in London, England.

Jon Hammlearned that meeting royaltycomes with its own set of unique rules.

The actor, 51, came face-to-face withKate MiddletonandPrince Williamat theLondon premiereofTop Gun: Maverickearlier this month, and revealed onThe Tonight Show with Jimmy Fallonthat there are “guidelines that are not so much guidelines as hard and fast rules that you are made to follow” when greeting a member of the royal family.

In a separate appearance onLive with Kelly and Ryan,Hamm said, “It’s a little anxiety-producing because they give you these rules that you’re meant to sort of follow. You’re meant to say, ‘Your Royal Highness’ — if they offer their name, then you can use their name, but you can’t do it first. And you can’t offer your hand, they have to offer their hand. Then you have to bow, but you can’t bow too low.”

“He geeked out a little onPrince William’s eyes,” Hamm explained to Fallon. “I remember coming back afterwards, he’s like, ‘They’re so blue. I got lost in his eyes.’ "

The actor then quipped, “I didn’t think we were allowed to look him in the eye.”

The monarchy has largely adapted to modern times and many people opt to greet theQueen Elizabethand other members of the royal family without much pomp — in fact, the British royal family’sofficial websitestates that “there are no obligatory codes of behaviour when meeting The Queen or a member of the Royal Family.” Still, there is a traditional form that many continue to follow to avoid a royal faux pas.

While it’s perfectly acceptable to simply shake hands when being introduced to a royal, men may opt to do a slight neck bow (from the head only) while women do a small curtsy.

On presentation to a member of the royal family, the correct formal address is “Your Royal Highness.” Then “Sir” or “Ma’am” can be used accordingly.

Prince William, Kate Middleton and Tom Cruise.

the UK premiere of Top Gun: Maverick at the Odeon Leicester Square, central London

Prince William, 39, went with a classic black tuxedo and bow tie.

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“We have a lot in common,” Cruise said of the prince at the premiere, according toMy London. “We both love England and we’re both aviators, we both love flying.”

source: people.com