"MIG" wrote

I think that's true, and can't really be solved. The lack of
crossovers on the route has always struck me, eg Catford to Atlantic.

Until the 1980s Victoria resignalling the Atlantic (South London) line ran
in glorious isolation all the way from Peckham Rye to Battersea Park with no
crossovers at all (and it could not be accessed from the Catford Loop at
Peckham Rye). Then four were put in (described for a journey to Victoria,
though the reverse facility is also available)
Crofton Road Junction (between Peckham Rye and Denmark Hill) : Catford Loop
to Atlantic
Shepherds Lane (between Brixton and Clapham High Street): Chatham to
Atlantic
Voltaire Road (between Clapham High Street and Wandsworth Road): Atlantic to
Chatham
Factory (immediately north of Wandsworth Road): Atlantic to Ludgate or
Stewarts Lane.

Peter