"MIG" wrote

Also, I think it may be earlier than that. I was an immigrant to
south London in about 1989, and I don't remember seeing the down
Stewarts Lane used in the early 1990s. Could just always be there at
the wrong time I suppose ...

My assumption was that Stewarts Lane only really started being used
much after Eurostar started sharing the tracks, the up track adding a
fourth track to the viaduct. Definitely one for Peter Masson.

Until the Victoria resignalling in the 1980s the high level route to
Victoria consisted of two up lines (from Shepherds Lane) and one down line,
with a 4-track approach only from Battersea Pier Junction. The Stewarts Lane
route was never used by passenger trains, unless there was an engineering
blockade or other problem on the high level route. I think people are right
in suggesting that use of the up Stewarts Lane route only began when
Eurostar started, and that use of the down Stewarts Lane route was very
rare - the only time I've used it was when there was a Victoria - Redhill -
Tonbridge service run by South Eastern, which ran from Chatham side,
crossing to the Battersea eversible at Stewarts Lane, and joining the
Brighton Main line at Pouparts Junction. With the Victoria resignalling what
had been the Up Slow on the high level viaduct became a reversible line, and
during the Eurostar era was mainly used as a Down Slow (the up slow being
the Stewarts Lane route).

Peter