It’s a grand gesture, and one that’s been around for as long as there has been a monarchy. And though it’s not mandatory to bow or curtsy to the Queen or a member of the royal family, many do it out of respect.  While it’s not limited to the United Kingdom and Commonwealth realms, it is rare to see an American do it.

“I curtsy to her every time I see her,” the Queen’s oldest granddaughter, Zara Phillips told Majesty Magazine back in 2008.  “The thing with my grandmother is she is still my grandmother and she’s very approachable, but she’s also from an era where that was how it was done. But there aren’t many people who know how it’s done. I know because I have grown up with it.”

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The Queen’s family always greets her first with a kiss, then with a bow or curtsy. Watch the royal family greet the Queen in the video below (specifically Phillips, her brother, Peter Phillips, and their step-father, Sir Timothy Laurence at the :19 mark)

In 2012, the Sunday Telegraph claimed the Queen sent out a memo reminding all family members about curtsying,  but the story wasn’t confirmed by the palace, who told People it was a “private matter” for the Queen.

Tldr; it’s complicated.  The Duchess of Cambridge is to curtsy to “blood royals” (Princesses Anne, Beatrice and Eugenie) when not with Prince William, for example

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“Updating the Order of Precedence has been a simple matter of following the precedent set when the Prince of Wales married Camilla Parker Bowles [in 2005],” a palace aide told the Telegraph at the time.

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Rumor has it that the royals can’t stand a deep, dramatic curtsy, but there are some (Margaret Thatcher, Joan Collins) who can’t resist taking a dip when they meet Her Majesty (can’t blame them).

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Well done, Carey Mulligan.

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It’s tradition for the royal bride to curtsy to the Queen after the wedding ceremony. Diana did it, as did Catherine, Meghan and Eugenie (though Diana’s, Catherine’s, and Eugenie’s were the only ones caught on camera).  The deep curtsy is elegant and a rare thing to witness.

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Debrett’s etiquette advisor, Jo Bryant advises anyone who meets a royal to “Put your right foot behind your left foot.  Briefly bend the knees with one foot forward keeping the upper body straight.  Repeat when the member of the Royal family leaves.”