A friend of mine lived with his mother in her flat until recently, when she moved out. Since then, he lives alone in his mother's flat, which she still owns outright. The council have changed the name on the council tax bill from hers to his - and are now demanding that he pay the council tax for the flat. My friend is refusing to pay it because he believes that it's his mother's obligation to pay it, because it's her flat and he's neither a tenant nor the owner. She is also refusing to pay it because she says it's not her duty to pay it because she no longer lives there. There's no rent, mortgage, landlord, lease, arrears, joint account or any legal agreement between him and her in regard to anything. He is currently the only person on the electoral register at the address. Who is legally obliged to pay the council tax on the flat in question?