Our elderly neighbours have a side window which they changed a few years before we moved in to this house from obscure glazed windows to clear. We rented this house for a short while before we bought it, and during the rental time they mentioned a few times that they hope we didn't mind that they had changed the window, it gives them a nicer view at the front of the house.
I do mind, because it gives them a view into our back garden which would otherwise be completely private. However, because it happened before we moved in or purchased the house and they are very elderly I don't think there is anything that can be done. When we come to change our side windows could we order clear glazed too, since they can't object? Alternatively could we lodge something with the council so that when their windows are changed next time they must be obscure-glass?