An out-of-date visa means the person is now in this country illegally, along with some half-a-million others, apparently. Does it sound like the house where he was living might have been a typical student let, perhaps with young men of various nationalities coming and going - like the one I have opposite me, where in the past six months we've had an Arab male, an African male, a Frenchman, several girls, and currently a very Rasta'd Levantine-looking gent who spends much of his time drawing with pen and ink?
Or is he actually drawing the specs for a bomb, and should I report the house to the Police, who'll find his visa is three days past exit, confront him, and shoot him?