Prince William and Princess Kate let one rule slide at Christmas for Prince George, Princess Charlotte, and Prince Louis.
According to a source who spoke to US Weekly, the rule the couple break is spoiling their children.
They said: “While Kate and William avoid overly spoiling the children, they let the rule slide at Christmas.”
The revelation comes as the country celebrates Christmas Day and families around the country engage in their own private traditions.
According to experts, there are a series of royal Christmas traditions that happen every year according to the walk to church at Sandringham.
Furthermore, there is another one which has been potentiall considered inappropriate by Miranda Holder.
She said that the royal tradition of weighing Christmas guests before and after their meal could still be continuing.
The tradition is allegedly linked to the idea that guests who have enjoyed themselves will have gained a lot of weight during the meal.
Speaking on TikTok, she said: “Okay, so this is one of the more unusual Royal Christmas traditions. We do love a bit of royal etiquette and eccentricity, particularly around Christmas time.
“But they have one Royal Christmas tradition that’s a little bit unusual, and definitely these days not very politically correct. They weigh their guests. Yes, you heard that correctly.
“They weigh their guests. The tradition reportedly dates back to King Edward VII, who thought it would be amusing to weigh his guests at the beginning and then at the very end of their stay for Christmas to see just how much they had enjoyed themselves.
“Food features heavily in the royal Christmas schedule, so the Queen thought it would be amusing to carry this tradition on.”
Ms Holder added: “Apparently, if you’ve put on 1.4 kilograms you’ve had a really good time.”
It is not known whether or not King Charles has engaged in the tradition this Christmas.
