In the 45 years since his investiture as Prince of Wales, Charles has created a unique role and career for himself as an activist on behalf of many causes. But is this activism compatible with the position of King? In Britain's constitutional monarchy, can Prince Charles remain an outspoken and passionate campaigner as he nears the throne, or should we expect a different style of monarchy in future, with a Royal Activist on the throne?
Elinor Goodman hears from close friends and colleagues of the Prince, as well as senior politicians with experience of how Prince Charles operates in Whitehall and beyond.
Producer: Jonathan Brunert.