10. A witness must be present when signing any royal decree.

Reason: In order to guarantee accountability and openness regarding the royal family’s conduct
Personal correspondence and unofficial documents are an exception.
All royal decrees must be signed in front of a witness for the sake of accountability and openness. Laws, declarations, and official documents are all subject to this regulation. It guarantees that there is some scrutiny and that royal actions are not made in a vacuum.
The signature of a witness is required for all royal decrees (@BBC iPlayer and Pinterest).
Usually, a high-ranking official or legal expert testifies. On the other hand, a royal signature can be appended to informal writings, such as letters or other non-official documents, without the need for a witness.