15/01/2018 17:30 SAST | Updated 15/01/2018 20:34 SAST

Why Meghan Markle Isn’t Allowed To Wear A Tiara Like Kate Middleton

Royal protocol strikes again!

Meghan Markle attends the Terrance Higgins Trust World AIDS Day charity fair at Nottingham Contemporary on Dec. 1, 2017.
Getty Images
Meghan Markle attends the Terrance Higgins Trust World AIDS Day charity fair at Nottingham Contemporary on Dec. 1, 2017.

If you've been keeping up with the royals, you might have noticed that Kate Middleton and Meghan Markle have very different fashion senses, from how they wear their hair to their choice of purse. But there's one style distinction that you may have been wondering about, and that's why the Duchess of Cambridge can wear a tiara, but Markle can't.

According to etiquette expert Grant Harrold, there's a simple explanation for this, and it all comes down to royal protocol.

"Only married ladies wear tiaras," he told BBC News.

Historically speaking, Harrold added, "It was 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."

This explains why Markle hasn't been spotted in a tiara just yet, whereas her future sister-in-law has been photographed sporting the family jewels on at least six different occasions, Glamour notes. Most notably, the duchess attended a diplomatic reception in 2016 wearing her late mother-in-law Princess Diana's favourite tiara.

Getty Images
The Duchess of Cambridge departs after attending the annual Diplomatic Reception at Buckingham Palace on Dec. 8, 2016.

But Markle won't have to wait too long to wear the the royal jewels. After all, she and Prince Harry will tie the knot in just four months' time on May 19, 2018.

And while it's assumed that Markle will sport a tiara for the first time on her wedding day — since the duchess did the same at her own nuptials in 2011 — that will also depend on royal protocol. According to Harrold, tiaras are an evening-only accessory.

"The old rule is that hats are never worn indoors after 6 p.m., because that is when the ladies changed into evening dress, and tiaras and the family jewels would come out," he explained to BBC.

Getty Images
Meghan Markle and Prince Harry visit Reprezent 107.3FM on Jan. 9, in London.

If Markle chooses to wear a tiara on her big day, royal expert Ingrid Seward says she'll have options to choose from, which includes a headpiece that belonged to Harry's late mother.

"She can choose something suitable, but she might also have the Spencer tiara, which is also Harry's heritage and is the one Diana wore on her wedding day," Seward told Us Weekly.

More From HuffPost Canada:

However, Markle is known to break royal protocols with her fashion, so there's a chance she may surprise us and don a tiara for the first time at a different occasion altogether.

The hype around seeing Markle in a tiara recently started building after a throwback photo of the former "Suits" star made the rounds on Twitter. The image revealed that the 36-year-old has actually worn a tiara before — and it was to her high school prom where she was named Homecoming Queen!

Clearly, Markle always knew she was made for royalty.

Keep Up With The Royals
Get our weekly email round-up of all things Royal.