In uk.transport.london Alistair Bell wrote:
Question then. ?When Broad Street was open it would have been a valid
London Terminal from Watford Junction. ?When it closed peak trains were
diverted by Graham Road curve of course which would have made Liverpool
Street a valid London Terminal,

At the time. But those services ceased before routeing was formalized
and 'Any Reasonable Route' became 'Any Permitted Route'.

Tickets to London used to be to 'London (SR)' from Surrey/Sussex/Kent
directions. What would have applied to the north of London, and would it
have divided the terminals you could have travelled to?

Theo