Northern line at Waterloo, about 6.30pm. I get on a tube that's reasonably busy - plenty of room to stand but no seats available. Driver pipes up after the doors have closed (successfully, after the first attempt).
"Please do not attempt to board or leave the train when the doors are closing, that's why they go
DING-DING-DING-DING-DING-DING-DING."
People are laughing and smiling with abandon, but like all good tube travelllers no-one makes eye contact with each other.
Very amusing.