If you feel you can't tell him to nick off, then another option is to keep a list of topics handy. When he questions you, look at your list of topics and pick one. He says...is that bloke living with you?........you say.......wow did you see that whale that beached itself in whatahoobey bay last week? Or....wow, you having trouble keeping up with the mowing, the grass here is really growing with all this rain.....Keep a huge list of possible topics and just keep blocking him.