No Turning Backs On The Queen
Mostly the rules that the royal family is bound to follow revolves around the Queen herself because she is the Queen, but this special rule makes it impossible for everyone to have their back towards the Queen, especially during her social interactions. It is the priority that she has the upper hand.
As he might have observed through the media that the Queen is always the first to leave, and there’s always a specific etiquette that applies to the people who wishes to interact with her; at these events, which include not speaking to the Queen until you are spoken to, and it is allowed under no circumstances to touch her, but Michelle Obama once broke this rule. She put her hand around the Queen for a photo.