If the monarch is also the head of the state religion that's kind of a priest/king sort of an arrangement, technically speaking. It's an interesting anachronism, that's all. I'm not arguing that the UK is an active theocracy.
Ha ha like the Aztecs, chopping off thousands of heads in the Tower of London to serve the dark and bloodthirsty entity that holds the British Isles in it's terrible thrall. That's quite a different take on merry old England.