Kate Middleton and Meghan Markle
Kate Middleton and Meghan Markle have to follow a strict dress code at Princess Eugenie's royal wedding. Pictured: Markle and Middleton attend the first annual Royal Foundation Forum held at Aviva on Feb. 28, 2018 in London. Getty Images/Chris Jackson

Princess Eugenie has a strict dress code for her royal wedding that Kate Middleton and Meghan Markle have to follow.

Latifa Yedroudj, a journalist for Express, recently revealed that all female attendees of Princess Eugenie's upcoming nuptials are expected to wear a hat. There is no exception, so the Duchess of Cambridge and Duchess of Sussex have to follow this protocol too. Even Queen Elizabeth II is expected to wear the accessory.

Meanwhile, Princess Eugenie and Princess Beatrice made a fashion faux pas in 2011 when they attended Prince William and Middleton's royal wedding in outlandish millinery. Prince Harry's ex-girlfriend, Cressida Bonas, admitted that choosing the right hat for a wedding is quite difficult.

Bonas was invited to Prince Harry and Markle's wedding. Days after the event, she wrote a blog about her struggles while preparing for such a grand celebration.

"Friends are starting to get married, which means the dilemma of British wedding attire. Hats," Bonas wrote. "Why do I find hats so tricky? Tricky to wear, tricky to look at, and extremely tricky for the poor soul sitting in the pew behind. Most of the time I avoid headgear. This can prompt disapproving looks from the older generations."

"Last weekend I attended the royal wedding. The invitation clearly stated that guests must wear hats. Yikes. I opted for a minimal feathered number — and can only hope I got it right," she continued.

Meanwhile, Richard Fitzwilliams advised Princess Eugenie to get an ideal wedding dress. The royal expert is hoping that the bride won't make a fashion blunder on her big day.

"There are members of the royal family who are style icons but this could not be said of Eugenie who has not distinguished herself in the sartorial stakes so far," Fitzwilliams told Express. "I think she will choose a delightful wedding dress and the wedding itself will be charming… Memories of Beatrice and Eugenie's outfits at William and Kate's wedding do die hard, so Eugenie must make sure she chooses the ideal wedding dress on her big day."

In related news, Prince Andrew reportedly requested BBC to air Princess Eugenie's royal wedding. However, the network refused to air the event as they believed that not enough people would watch it.