In the UK (and USA) officials are elected by their constituants and represent the wishes of that community. Thus the majority populace legally elect their own officials. Sharia Law is now adopted into the British Legal system. Some cities legally bar non believers from entering those designated areas posted with "Sharia Law
Islamic law is adopted by British legal chiefs - Telegraph
This is a factual response to a question raised on this thread of "why" and is not a slur or insult aimed at anyone. To quote Rodney King "Why can't we all just get along"