While there are many royal guidelines the royal family members must adhere to, this one takes a whole new shine.
Becoming part of the royal family has its restrictions, based on its traditional rules the monarchy has lived by for centuries. And while many of the rules are publicly known and displayed, there is one particular rule that Kate Middleton and Meghan Markle live by that has gone under the radar in the public eye.
Being royals, the Duchess' always look glamorous - sporting elegant outfits and having royal accessories to match. And as such, their priceless jewels have masked the one thing that we haven't seen: diamonds before dinner.
A guideline that has been passed through the monarchy for generations, royal women are to leave their diamonds at home before they attend day-time public events, as it's seen as 'inappropriate' to wear them for such casual affairs.
"Before 6pm, you'll see metallics, gemstones, pearls and sapphires," etiquette expert, Myka Meier told News.com.au.
"At night, you'll see the diamonds come out, and that's in order to not come across as flashy in your appearance," she told the publication.
However, the royal women are allowed to wear their engagement rings should they have diamonds.
It's believed that diamonds and other statement sets and pieces are only appropriate for dinner occasions, stately affairs and important events such as weddings, where it's important to showcase your royal stature.
During the day, it's encouraged that the royals wear minimal jewels and present themselves in a more reserved manner, which you'll notice with the Duchess' day wear.
Kate Middleton keeps it simple, wearing only the famous sapphire engagement ring that belonged to Princess Diana and a set of drop earrings, while Meghan Markle chooses fine jewellery and even had her diamond engagement band resized smaller.