A thing that I wonder about

Tea comes to England. If you have tea or coffee, you know they can stain mugs. I've pretended not to see them, but I don't like brown inside. I used to use a magical melamine sponge and sometimes dish bleach in Japan. I wonder how do British people remove tea stains? I can't find proper cleaning substances at a supermarket in the UK. If the tea is/was the most quintessential of English drinks, I think they should invent or produce a method of removal as the easiest and quickest removers:)