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Cara Delevingne -

The English model turned heads because of her outfit choice at Princess Eugenie's wedding in 2018. Delevingne wore a tailcoat suit and a top hat, breaking royal wedding dress code.

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Cara Delevingne -

Though it looks like she checked with the bride first. "Eugenie has been a friend of mine since I was a kid and I've always wanted to wear tails ... I texted her, as I wasn't sure about it and she was like: 'Of course, I expected nothing else from you!'" explained Delevingne.

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Cara Delevingne -

Still, the rules for wearing a top hat say that it should be carried, not worn, inside the church. But it looks like the model didn't get the memo. And, surely, a toothpick is not an acceptable accessory.

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David Beckham -

The former soccer star wore his OBE (Order of the British Empire) medal on the wrong side, at the wedding of Prince William and Kate Middleton in 2011.

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David Beckham -

Guests at British royal weddings are also expected to wear clothes designed in the country. Instead, Beckham wore a suit by American designer Ralph Lauren.

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Liv Tyler -

It's common knowledge that one should not wear black, or indeed very dark clothes, to a wedding. Liv Tyler seemed to disregard this rule at Princess Eugenie's wedding.

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Naomi Campbell -

And so did Naomi Campbell. The former supermodel's black ombre dress and cape from Ralph & Russo looked amazing, but was probably suited to another event, not a wedding.

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Victoria Beckham -

Victoria Beckham clearly likes to wear somber hues to royal weddings. Navy was her color of choice for both Prince William's (left) and Prince Harry's (right) weddings.

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Carey Mulligan -

The actress failed to wear a hat for the wedding of Prince Harry and Meghan Markle.

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Carey Mulligan -

Instead, Mulligan wore a white-feathered hair clip. It looked great, but it was not quite a fascinator.

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Princess Beatrice -

It's good etiquette to not wear anything that draws too much attention away from the bride. Princess Beatrice's choices of hats are anything but discreet, as you can see by the fascinator she wore to Peter Phillips and Autumn Kelly's wedding.

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Princess Beatrice -

But the one Princess Beatrice wore to the wedding of Prince William and Kate Middleton was the one that got mocked extensively on social media.

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Patrick J. Adams and Troian Bellisario -

Meghan Markle's former 'Suits' co-stars broke protocol when they did a seemingly innocent thing: they took selfies.

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Troian Bellisario -

"Guests will be told not to take pictures at any [part] of the day," explained Duncan Larcombe, former Royal Editor of The Sun. And one more thing: open-toe shoes are a no-no at royal weddings, as they are considered too informal.

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Naomi Campbell -

The actors were not the only ones posting selfies on social media. Naomi Campbell also did so, from inside Princess Eugenie's wedding!

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Robbie Williams -

The singer did a very frowned-upon thing at Princess Eugenie's wedding: he chewed gum!

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Ayda Field -

Field joined her husband Robbie Williams in breaking protocol by wearing a white Armani skirt suit to Princess Eugenie's wedding.

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David Beckham -

Robbie Williams was not the only one caught on camera with gum in his mouth. David Beckham was caught chewing gum at Prince Harry and Meghan Markle's wedding.

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Sabrina Dhowre Elba -

Idris Elba's wife's Gucci ensemble looked gorgeous at Harry and Meghan's wedding, but perhaps it was a bit too informal for the occasion.

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Sabrina Dhowre Elba -

Elba was also wearing a white dress underneath, which is obviously a no-no at a wedding.

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Joss Stone -

The singer's choice of dress was also criticized for being too white. Plus, Stone wore a white fascinator.

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Pippa Middleton -

And then there's Pippa Middleton, who wore white to her sister's wedding. Royal bridesmaids typically wear the color, but she could have worn something less bridal. Though, apparently, the look was meant to be coordinated with Kate's.

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Pippa Middleton -

Plus, Pippa was named her sister's maid of honor. Traditionally, most royal brides do not have adult bridesmaids.

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Chelsy Davy -

The ex-girlfriend of Prince Harry broke a number of dress code rules at his wedding. She wore open-toed shoes, an above-the-knee dress, and bare legs. Plus, Davy wore a dark dress.

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Chelsy Davy -

The businesswoman stuck with navy for Princess Eugenie's wedding, but at least she covered her knees and toes.

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Prince William -

Prince William broke protocol when he named his brother, Prince Harry, as his best man. Traditionally, royal bridegrooms chose a 'supporter' instead of a best man.

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Prince Harry -

And then Prince Harry did the same when he named Prince William his best man.

Sources: (Nicki Swift)

See also: The British royal family's strict marriage traditions

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