The royal family have several Christmas traditions which have been in place for centuries.
Christmas in the royal household always takes place at the Queen's residence in Sandringham, and members of the British monarchy are expected to attend.
This year will be the first Christmas the newly-minted Duchess of Sussex will celebrate with the royals.
Meghan Markle, 36, will partake in several unique traditions - including opening presents on Christmas Eve and attending church twice on Christmas Day.
But the most bizarre formality of the day will be when the Queen weighs her guests before and after the Christmas feast.
According to royal expert and editor of Majesty magazine Ingrid Seward, the Queen will ask Meghan to weigh herself before the feast on a pair of antique scales when she first arrives.
She will then be weighed again after Christmas dinner and lunch, The Sun reports.
It is reportedly a method to ensure all her family members are 'well fed' during the Christmas festivities.
Even Prince William, Prince Harry and Meghan's mother Doria Ragland will be asked to participate in a weigh-in!
The odd tradition reportedly dates back to King Edward VII's reign in the early 1900s, and the royal family has followed it ever since.