Prince George's birth certificate disclosed a huge revelation about Kate Middleton

But it makes total sense, obviously...

But it makes total sense, obviously...

Have you ever wondered why the Duchess of Cambridge isn’t simply called Princess Catherine or Princess Kate (like Princess Diana), seeing as she’s married to Prince William?

Well, if you've ever stopped to take a look at Prince George's birth certificate (which fair enough, you probably haven't) you'll see that the Duchess of Cambridge is actually listed as 'Catherine Elizabeth Her Royal Highness, the Duchess of Cambridge.'

Credit: Getty Images
(Image credit: AFP/Getty Images)

What's even more interesting is if you take a closer look at Kate's occupation, you'll see 'Princess of the United Kingdom' listed down - which does sound pretty damn cool, TBF.

So why doesn't Kate refer to herself as a Princess, instead choosing to go by the title the Duchess of Cambridge?

Well, wonder no more, because we’ve got the logical explanation.

When she married Wills in 2011, she was given the title of Duchess of Cambridge, however her lesser known name is Princess William of Wales, as women marrying into the royal family take their husband’s name. A bit archaic, we know.

Her full title, to be precise, is Her Royal Highness Princess William, Duchess of Cambridge, Countess of Strathearn, Baroness Carrickfergu.

But according to CNN royal expert Victoria Arbiter, the 'Duchess' title is more important, hence why she uses it.

She told Yahoo Style: ‘While Catherine is absolutely a Princess, her correct title is ‘Her Royal Highness the Duchess of Cambridge. She wasn’t born a blood Princess, so she is not a Princess in her own right. When she married William, she took on the rank of her husband, a royal Prince. However, referring to her as ‘Princess Kate’ is simply incorrect.’

As Prince William is also a Duke, and that is his more important title, Kate assumed it herself.

This kind of makes sense, so why was Princess Diana a Princess? Well, again, it was down to her husband Charles.

Charles is a Prince twice over, as he was born one and he was made one (Prince of Wales) in 1969. That second title is the more important of the two, so Diana took the title of Princess.

Fair enough.

Penny Goldstone

Penny Goldstone is the Digital Fashion Editor at Marie Claire, covering everything from catwalk trends to royal fashion and the latest high street and Instagram must-haves.

Penny grew up in France and studied languages and law at the Sorbonne Nouvelle University in Paris before moving to the UK for her MA in multimedia journalism at Bournemouth University. She moved to the UK permanently and has never looked back (though she does go back regularly to stock up on cheese and wine).

Although she's always loved fashion - she used to create scrapbooks of her favourite trends and looks, including Sienna Miller and Kate Moss' boho phase - her first job was at MoneySavingExpert.com, sourcing the best deals for everything from restaurants to designer sales.

However she quit after two years to follow her true passion, fashion journalism, and after many years of internships and freelance stints at magazines including Red, Cosmopolitan, Stylist and Good Housekeeping, landed her dream job as the Digital Fashion Editor at Marie Claire UK.

Her favourite part of the job is discovering new brands and meeting designers, and travelling the world to attend events and fashion shows. Seeing her first Chanel runway IRL at Paris Fashion Week was a true pinch-me moment.