I would think that a head of state with substantial assets administered by the government and a massive public subsidy for the royal family would be in a positi

I would think that a head of state with substantial assets administered by the government and a massive public subsidy for the royal family would be in a position to lobby the government. The ruling party in the UK at the moment is pretty favorable to the monarchy so it isn't surprising they would provide the monarch with some ability to lobby the government. I'm not a royalist or British but I would be more concerned about the financial subsidy and the ruling party's deference to the monarchy than the theoretical possibility of them witholding consent. It isn't much of a negotiation if one side can immediately win though right? The prime minister can just threaten to go public that he can't obtain consent and the monarch has to back down immediately.