When it comes to meeting a member of the Royal Family, there are a whole load of rules and regulations that you have to follow.
This goes for everyone, whether you're a lowly peasant all the way up to celebrities and world leaders.
But despite many celebrities meeting members of the Royal Family, many of them ended up making something of a royal faux pas during their meeting.
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The rules cover everything from how you are supposed to greet the member of the Royal Family, as well as how you address them and how you behave around them.
There are any number of reasons for these, some of them being tradition but others potentially being about safety.
However, some people have flouted the rules during their meetings with a member of the Royal Family.
Not only that, but they got away with it! So, who are they?
Roger Federer
When the tennis legend met Kate Middleton in the royal box at Wimbledon he passed over the more traditional greeting.
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Instead, he greeted her by placing a hand on her back, flouting the 'no touching' rule which says you should never touch them unless they initiate contact, like extending a hand for a handshake.
Still, Federer is known to be pals with Kate's sister Pippa, so is on more familiar terms than most.
Joe Biden
When the incumbent US president met the late Queen Elizabeth II on an official visit, he donned sunglasses.
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According to one royal butler, this breaks the rules as eye contact is important in a formal introduction.
I'll leave it up to you to decide how much the leader of the USA should give a hoot about British royal traditions though.
Didn't they start a war over that a few years back, like 1775 or something?
Donald Trump
It's perhaps not surprising that a man of Donald Trump's social sophistication managed to break the rules while meeting the late Queen.
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In his case, it was because he went for a handshake instead of bowing, and then proceeded to walk ahead of the Queen when tradition says she should be in front.
Allison Janney
The actor recalled how she had greeted Kate Middleton by running up to her bare foot, and calling her 'honey'.
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Speaking to James Cordon on The Late Late Show, she said: "I called her 'honey' and that might not have been royal etiquette."
Ed Sheeran
No excuses about not knowing the custom for British musician Ed Sheeran, who touched the future King Charles on the arm.
Fortunately it didn't seem to have too bad of an effect, as Sheeran recalled: "He was asking me if I was still selling lots of records and I told him I've got a concert in New York tomorrow, and he was quite surprised I was flying after this."
LeBron James
When the basketball legend met with Prince William and Kate Middleton, he broke the 'no touching' rule by putting his arm around them.
Despite this, insiders have said that royals sometimes like protocol being broken as it mixes things up a bit.
Michelle Obama
In a similar mishap, the US first lady at the time Michelle Obama placed a hand on the Queen's back during a visit.
Recalling the encounter, she said: "I then did what's instinctive to me anytime I feel connected to a new person, which is to express my feelings outwardly. I laid a hand affectionately across her shoulder."
It wasn't until after that she realised it could be something of a faux pas, but it seems that the Queen was okay with it.
The former first lady said: "I daresay the Queen was okay with it, too, because when I touched her, she only pulled closer, resting a gloved hand lightly on the small of my back."
Topics: UK News, Celebrity, US News, Royal Family, The Queen, King Charles III, Kate Middleton
Kit Roberts