12. A proposal cannot be made without approval.

Justification: The 1772 Royal Marriages Act
Exception: No, if married without it, they lose their place in the line of succession.
The Royal Marriages Act, which established guidelines for royal engagements, marriages, and other events, was passed in 1772. One important tradition that is still in place today is that royal descendants must first get a monarch’s permission before making a proposal.

A proposal cannot be made without approval. ©Max Mumby/Getty Images/Indigo
Before making a proposal, Prince William and Harry had to seek Queen Elizabeth II’s approval. Going forward, future royal weddings will need to go via King Charles. To ensure no marriage lowers the House of Windsor’s prestige, the Royals have this restriction. There are still articles from the early 1980s New York Times archives discussing the “pros” and “cons” of Charles’ proposal to Diana.