A Serbian beggar, fed up with being ignored, has apparently taken to placing his cap and shoes on the pavement, together with a sign saying "invisible beggar" (fair enough, although I think that "hungry, homeless and invisible" might have been even more poignant). But it's working, for nowadays he sits in the cafe opposite and watches the cap fill up with money.
This is an inspired idea. We've all come across the invisible policemen (most of them, especially when you need one), and the invisible train manager who makes unintelligible announcements from the region of the ceiling, and the invisible traffic warden, who manages to stick a notice to your car windscreen in the time it takes to nip out and buy a packet of Polos, although you never see him.
What invisible job would you like? I think I'd like to be the invisible writer in residence at some very prestigious seat of learning. I would, of course, consent to become visible, on request.