MIG wrote:

I've noticed that for the last year or so the Olympia line has finally
been taken off the internal diagrams in the C stock, which never went
there as far as I know.

District Line Working Timetable number 125, which was used from 28th
September 1997 until 26th September 1998, had alternate Edgware Road trains
in the morning peak serving Wimbledon and Olympia. I have no idea how many
years this arrangement lasted.