At Westminster Abbey's Commonwealth Day service, Kate Middleton missed curtsying to Charles & Camilla.

Royal fans noticed this and were confused as Kate usually curtsies to them.

The reason for skipping the protocol has been disclosed by Cheat Sheet publication.

Female family members must curtsy before the King and Queen Consort only once a day.

This suggests that Kate might have seen her in-laws earlier that day before the official event.

Female family members must bow before the King and Queen Consort only once a day.

The royal family adheres to strict etiquette and procedure.

Kate is known for her impeccable style and grace.

Kate and William are popular among the public and are considered to be modernizing the royal family.