Whether or not Mountbatten “deserved” to die, as Novella thinks, is also irrelevant here, as he wasn’t killed because he was an abuser. His boat was bombed, and several people killed, because he was a close relative of the UK Head of State, and his death was intended to be a political act. Therefore demonstrating that given the UK’s history of violent acts towards people in public roles, any head of state, and their family, would need protection at the same level the incumbents do, including when they leave office. So claiming that the public purse would save on security costs if we no longer had a royal family is illusory.