"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.)

I've always liked to imagine that they have adjustable colour-coded signs
there. When the sparse service of Piccadilly Line trains is due, they change
them to blue. When the last Piccadilly train has gone, they turn'em green.

Sorry.
I'll go now.