Ian Jelf wrote:
I was on a late night Piccadilly Line train which stopped at Turnham
Green the other, er, night.

I've often wondered, what's the story behind that oddity? How did it
come to be a feature of the timetable? (I can think of no parallel
elsewhere on the system, at least not in even remotely recent years.)

Late Met trains stopped at Willesden Green and Neasden not too long ago....
I think that has stopped now.