Daena explained: “More recently, the Duchess of Cambridge has bent this rule and taken off her coat whilst attending indoor events.”

Other important royal style rules have to do with the colours members of the Royal Family choose to wear when travelling abroad.

The expert said: “Whilst touring abroad, royal protocol dictates that royal women also honour local history and traditions by sporting the colours of the country they are in.”

They can also do so by “wearing jewellery gifted to the Queen by that country or respecting local customs such as covering the head with a scarf”.