The British royal family has a long-standing dedication to rules and protocol, and what they wear is certainly no exception. In fact, some things cannot be worn by the Duchess of Cambridge or the Duchess of Sussex before 6 p.m. What is off-limits to Kate Middleton and Meghan Markle when it comes to their fashion choices?

Toyal expert Myka Meier revealed to News.com.au that neither Kate nor Meghan are "allowed to wear diamonds before 6 p.m." This is due to the fact that wearing them early in the day could be seen as "flashy." However, noted the authority, other jewels, such as gemstones, pearls, and sapphires, are approved to be worn at any time of the day.

"At night, you'll see the diamonds come out, and that's in order to not come across as flashy in your appearance," she also stated. Additionally, it has been said that both Meghan and Kate have their own "team of aids" to help them get dressed and make the right fashion choices, which would of course include decisions based around their jewelry.

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This protocol may be an explanation for why you are more likely to see the royals wearing "more affordable" jewelry during the day as they go about tending to their royal duties. However, when it comes to tiaras, it's a bit of a different story.

As noted by Grant Harrold, who served as a former butler to Princess Diana, the pieces are usually reserved for members of the royal family and are to be worn as a "sign of status." Additionally, tiaras were also used to symbolize that you were "taken and not looking for a husband." 

As for the events that diamonds are most likely to be seen at, Harrold shared that the more "significant" the event, "the more likely you are to see them wearing diamonds - specifically when there is a reason."

Kate Middleton, Meghan Markle Catherine, The Duchess of Cambridge stands with Meghan, Duchess of Sussex at Westminster Abbey for a Commonwealth day service on March 11, 2019, in London, England. Photo: Getty Images/Richard Pohle