Kate Middleton, Meghan Markle
Kate Middleton and Meghan Markle were only spotted wearing a tiara after their respective weddings. Pictured: Middleton, Markle attend day twelve of the Wimbledon Lawn Tennis Championships at All England Lawn Tennis and Croquet Club on July 14, 2018 in London, England. Getty Images/Clive Mason

Kate Middleton and Meghan Markle are only allowed to wear a tiara after 6 in the evening.

Grant Harrold, a former royal butler, told The Sun that the rule applies to all female royals. However, there is also an exception to the rule. For instance, Markle and Middleton tied the knot with Prince Harry and Prince William, respectively, before 6 p.m. Since royal weddings are special events, they were allowed to wear a tiara to their big day.

Harrold said that the rule was created since diamonds are also only worn together with a female royal’s evening attire. Tiaras may only be worn by married royals or those that are about to tie the knot.

“For married ladies, it is a sign of status and would show you were taken and not looking for a husband. For the gentleman, it was a clear sign not to make advances toward the lady in question,” Harrold said.

Harrold also said that Middleton and Markle may wear diamond jewelry during the day, but they normally reserve the lavish accessory during more special occasions.

“The more significant event, the more likely you are to see them wearing diamonds – specifically when there is a reason,” he said.

In related news, Princess Eugenie has not been spotted wearing a tiara even though she’s been part of the royal family since birth. This is because is still single. Prince Andrew and Sarah Ferguson’s youngest daughter will wed Jack Brooksbank on Oct. 19, and she is expected to wear the headpiece to the formal occasion.

Geoffrey Munn, a jewelry expert, told Cosmopolitan, “Any woman may wear one, but ancient tradition has it that they must be a bride or already married. The tiara has its roots in classical antiquity and was seen as an emblem of the loss of innocence to the crowning of love. One of the mainstays of European royalty and aristocracy is to do what you have always done and formal dresses, jewelry, and tiaras are just a part of this.”