When ol' Lizzie died, the Archbishop of Canterbury let us all know that God dropped him a message to say the King Charles should succeed to the throne, which worked out awfully lucky with what was already being planned. The Head of State of the United Kingdom is claiming to derive their authority from God (aka Divine Right of Kings), state and church are officially unified and clerics are a required part of the legislature, does that not make it a Theocracy by any reasonable definition?
Yeah.
It's also a state that should've cut its royals' heads off a long ass time ago.