peter wrote

Perhaps because Southeastern don't go to Vauxhall. *;-)

My mistake. I meant, of course, South Western. But then I still
think
of it all as Southern Region.

Theoretically an announcement and/or display could have been made on
the SWT train, on Vauxhall NR or on Vauxhall LT but since the last
didn't happen or was ineffective in changing behavior (since you got as
far as Pimlico) the chances of getting an effective message to those
outside TfL seems small.

--
Mike D