"MIG" wrote

To sum up, i think building those platforms would be a good idea, to add
flexibility and resiliency to the network, and to serve local users
better, but i don't think they're going to deliver extra capacity.

I once had a commute from Swanley to South Bermondsey, and the connection at
Peckham Rye worked well enough. From Chatham itself to London Bridge the
best route is the direct train, or backtracking from Cannon Street if the
fast doesn't stop at LB, although it's a bit slow via Dartford off peak.
From intermediate stations I would take the tube Elephant.

For your other example of Lewisham to Herne Hill I would take a bus from
Denmark Hill, or change at Peckham Rye and walk from North Dulwich.

Loughborough Junction must have been quite a hive of activity when it had
six platforms (2 on the Herne Hill line, two on the Denmark Hill spur - the
remains are still extant, although they haven't been used for at least 90
years - and two on the spur towards Brixton. One of the bronze commuters is
silently waiting on the remains of the Catford Loop platform at Brixton).

I don't think South London line platforms at Loughborough Junction can
really be justified, though platforms on the South London (Atlantic) lines
at Brixton would be well used, though expensive to provide on the viaduct.

Peter

I can see that it's limited, but it's also cheap, and therefore
possibly possible.

And I was thinking about journeys south as well. For example, going
from Lewisham* to Herne Hill really needn't be as difficult as it is.
To do it by train you'd have to clutter up routes into London Bridge
and Blackfriars or Victoria and back out again, when a change at
Brixton or Loughborough Junction would make it simple.

Given the enthusiasm for orbital routes, which I don't entirely share,
surely it should be possible to come in from one direction and travel
along the orbital route a bit before proceeding in or out on another
radial route, thereby benefiting those who don't live directly on the
orbital corridor.

*The route to Victoria has so many signal stops, there might as well
be lots of stations with no effect on journey time.