It was indeed on a C-only (well, Y and C only) A340. Still, there *is* a lavatory there, and nothing at all indicates that it is crew-only. Like I said to F/As then, I would have gladly used another lavatory had I been told in advance, or had I seen signage to that effect. You can't expect people to follow unwritten rules about such specific restrictions.

I've just written to LH customer service about this, including asking whether this is a policy, and if it is, to make it explicit. I don't expect any substantial reply other than some sort of canned statement, but it doesn't matter really as I will continue avoiding LH anyway. Too bad because when I flew LH, I chose them over other airlines.