Good morning, Mr. Davy. Going...down?

They're renovating the building our offices are in at the moment, and what this basically means is that there aren't any working toilets until six floors above us so every time nature calls it is calling from quite a distance rather than just down the end of the corridor as normal.
Being a lazy sod busy and dynamic executive without much time, I get the lift rather than use the stairs. No problem there, you might think, until yesterday afternoon when coming back down to our floor I found myself stuck alone in the lift with a man who silently stared at my crotch for the entire trip.
This is a remarkably disconcerting experience. Not only did I spend the trip wondering if he was a whacko or if I'd dropped an eye-catchingly large dollop of Piccalilli* into my lap from my lunchtime sandwich (I hadn't, thankfully), but also it made the trip last twenty five minutes rather than the usual thirty seconds.
Having someone staring in a personal way is offputting to say the least, and so all the witty things I thought of to say in the situation occurred to me about a half-our later ("I bet you've never seen one like that before, eh?", or "Whatever you do, don't make eye contact!") when it was far too late. What it did get me thinking about, however, was what the social rules for sharing a lift with strangers are.

[Poll #797701]

^{*"Excuse me, you seem to have a lump of onion stuck to your crotch."
"That's not onion."
"Oh. Right. Goodbye."}