The Strict Tiara Rule Meghan Markle, Kate Middleton, and Princess Eugenie Must Follow

Tiaras are great and all (okay, really great), but just because the Queen hand-gifts them to you from her vault doesn't mean you can wear them anytime you want. According to Grant Harrold, famous royal etiquette expert in the U.K., Meghan Markle, Kate Middleton, and now Princess Eugenie actually have to follow a strict rule when it comes to the accessory: They can't wear their tiaras before 6 p.m.

It may sound intense, but that's because they are dealing with very special jewelry. Meghan's royal wedding tiara, Queen Mary's Sapphire Bandeau that comes straight from the Queen's vault, was originally made in 1932 for the Queen's grandmother and the brooch dates back to 1893. On her wedding day, Kate Middleton wore the Cartier Halo tiara, which holds nearly 1,000 diamonds. Princess Eugenie stunned in an Greville Emerald Kokoshnik tiara.

Of course, this rule has an exception during special pre-6 p.m. events like royal weddings, but otherwise all royals need to keep their tiaras in their collections strictly until the evening since diamond tiaras are technically considered formal wear. Kate was spotted in December wearing the Cambridge Lover's Knot tiara, a favorite of Princess Diana's, to a diplomatic ball in the evening.

Tiaras are reserved for married women, which means Princess Beatrice hasn't been allowed to wear one yet. Her sister, Princess Eugenie, joined the married royals club on October 12. Eugenie was expected to wear the York Diamond tiara, which was gifted to her mother, the Duchess of York, on her wedding to Prince Andrew in 1986 by the Queen and Prince Philip. However, she surprised royal fans and wore the Greville Emerald tiara, which was originally created in 1921. It came straight from the Queen's vault.