Kate Middleton and Meghan Markle
Kate Middleton and Meghan Markle have to follow rules when wearing jewelry. Pictured: Middleton and Markle applaud ahead of the Ladies' Singles final match between Serena Williams of The United States and Angelique Kerber of Germany on day twelve of the Wimbledon Lawn Tennis Championships at All England Lawn Tennis and Croquet Club on July 14, 2018 in London. Getty Images/Michael Steele

Kate Middleton and Meghan Markle have to follow another royal rule when it comes to wearing jewelry.

The Duchess of Cambridge and Duchess of Sussex are not allowed to wear their bling anytime they wish. The royal family has a set of rules when it comes to this. According to Myka Meier, Middleton and Markle are not permitted to wear diamonds except for some special occasions. In addition, there are suggestions as to what type of jewelry to use in a particular moment.

"Other jewels are worn pre-6 p.m.," Meier said (via Express). "Before 6 p.m., you’ll see metallics, gemstones, pearls, sapphires. At night, you’ll see the diamonds come out, and that’s in order to not come across as flashy in your appearance."

Middleton has been seen wearing a variety of jewelry from the Queen's vault. A few weeks ago, the duchess was spotted with Queen Elizabeth II on their way to attending a church service. During the sighting, Middleton wore the monarch's Bahrain pearl drop earrings.

Prince William's wife also borrowed the Queen's Cartier Halo tiara when she walked down the aisle. In 2017, Middleton wore Queen Elizabeth's four-strand pearl choker with a central diamond that was commissioned using a collection of cultured pearls.

On the other hand, Markle was seen wearing a pair of diamond earrings during a recent engagement with Prince Harry. According to the publication, it was a gift from Queen Elizabeth II.

In related news, there are concerns that the new royal might feel suffocated with the royal lifestyle. The members of the Firm have tons of protocols that even Princess Diana find absurd.

"You can set your watch by the royals: every year, Balmoral in the summer, Sandringham at Christmas, Windsor at Easter," royal biographer Duncan Larcombe said.

"Supposing Meghan was like, we've been here for 48 hours now and I'd really like to be on a beach in Saint Tropez, if she doesn't like it, it's going to be really difficult for her. It would be really suffocating. No one spends months of the years on holiday with their parents and their grandparents on holiday," he added.