in an announcement after the death of queen elizabeth ii, prime minister liz truss called charles king charles iii. this was the first time anyone had used that name officially. shortly afterwards clarence house confirmed that he would use the regnal name "charles iii". when a british monarch becomes king or queen, they are allowed to change their name if they want to. for example, charles' grandfather changed his name from "albert" to "george", and he was "king george vi".