Kate Middleton is known as one of the more by the book royals. Little did fans know, she's been breaking royal rules all along -- or at least since she married Prince William. 

The future Queen of England has become a worldwide style icon. From her hair to her shoes, she's got the whole royal look down. She does all of this while keeping in line with the royal dress code, except when it comes to one thing: her nails. 

The apparent rule of thumb for nail polish is that royals only wear clear or neutral polish. This is a rule that Kate follows on her hand, but when it comes to her toenails, the Duchess of Cambridge prefers a deep red. According to AOL, photographs dating as far back as 2012 show her sporting this choice of color. 

Of course, some people, like Marlene Koenig, a historian and writer, told T&C that there are "no books or rules about what polish shade a royal can wear." There has never been an official handbook -- that we know of -- published about royal rules and protocol, but if Kate did, in fact, break a rule, it wouldn't be the first time. 

The 37-year-old plans to bend the rules when it comes to fulfilling her royal duties. Typically Kate and Prince William could be gone, away from their kids for potentially weeks on end while on their royal tour but they have chosen to do things differently. The Duke and Duchess of Cambridge will likely not spend longer than one week away from their little ones.