Question them if that's possible, otherwise knock them out, either with the fisticuffs or the assistance of a nearby object capable of causing intense trauma with relative ease. Then I'd call the police or take whatever necessary action to exact justice as it's due.
At least, that's what I'd normally (intend to) do but if it's somehow possible, I'd politely greet them with a handshake, saying "why hello there, care for a cup of tea?"
I would sit them on the couch and persuade them to say yes - if they ask for crumpets though I'll remind them this isn't a charity - and go into the kitchen to fix them a cup. And in the kitchen, I'll call my immediate family. When I come out shortly after, I'll be carrying a knife to ensure I have the upper hand. At that moment, I'll state that this isn't their cup of tea, just as their demeanour here isn't mine. That would be checkmate, and reinforcements would eventually arrive home.