Why Meghan Markle and Kate Middleton wear tiaras, but Beatrice and Eugenie can't.

Princess Beatrice and Princess Eugenie have never been seen in the most glamorous royal headpiece there is. Whilst Kate Middleton and Meghan Markle have both stunned in diamond tiaras, the Queen’s very own granddaughters have never had the honour.

The Duchess of Cambridge has donned traditional tiaras only on very special occasions: her wedding day in 2011, and at a white-tie party last year at Buckingham Palace.

Meghan Markle, the newest member of the royal family, has even been able to wear one of the traditional headpieces before Princesses Beatrice and Eugenie, at her wedding to Prince Harry in May of this year.

So it does seem a little odd that the Duchess of Cambridge and the Duchess of Sussex should wear tiaras to special occasions, whilst the two princesses born into the monarch have not.

But the reason why is quite simple: Tiaras are reserved for married royals.

With Princess Eugenie getting married in October to Jack Brooksbank, she is expected to wear a diamond headpiece much like her cousin-in-laws, as traditionally royal women will wear a tiara for the first time on their wedding day.

According to People, Princess Eugenie is widely anticipated to wear the same tiara her mother, Sarah Ferguson, wore on her wedding day to Prince Andrew.

But until then, Princess Eugenie and Princess Beatrice will have to stick to their fanciful hats that they're known for.