The formation of the Southern Railway brought the management
of three large and extensive suburban networks under one organisation. Both
the LSWR and LBSC were joined by the lines of the South Eastern & Chatham
Railway. The Southern decided to expand the electrification on the two former
and commence work on electrifying the latter. But first it had to decide
on which system to adopt as standard for future electrification work. Not
surprisingly it chose the LSWR third rail system as the Southern Railway
management was dominated by ex-LSWR managers. The decision did not prevent
the completion of the last LBSC electrification to Coulsdon North and Sutton
in 1925 but it meant that before the equipment was run in it would be
replaced.
Work first began on adding to the LSWR electrified lines
and the former SECR routes. On July 12th 1925 the LSWR routes from Raynes
Park to Dorking, Claygate to Guildford and the section that joined these
between Effingham Junction and Leatherhead were opened to electric traction
with the SECR routes from Orpington to Victoria via Penge East and to Holborn
Viaduct via Nunhead along with the branch from Nunhead to Crystal Palace
(High Level) on the same date. Thus began the Southern Railway's tireless
spread of suburban electrification with the third rail.
By the end of July 1926 all the routes from Dartford to
Charing Cross and Cannon Street along with the lines from Lewisham to Hayes,
Addiscombe and Orpington had been added. With the inner suburban routes of
former LSWR and SECR completed attention turned to the LBSC lines still running
with the original AC overhead electrification.
The electrification of these lines involved equipping
some routes from new with third rail and also replacing the overhead system
with DC third rail on lines so equipped by the LBSC. In the case of the later
the overhead was kept in operation throughout the work on laying and connecting
the third rail and was not switched of until the DC system was ready to come
into use, thus providing, on the whole, a seamless changeover. During 1928
and 1929 the routes from London Bridge to Crystal Palace (low level),Caterham,
Tattenham Corner, Victoria (South London Line), Coulsdon North, Epsom Downs,
Norwood Junction, Selhurst & Epsom were either electrified from new or
converted to third rail. In addition the lines from Wimbledon to Herne Hill
and South Merton were electrified leaving only those lines from Victoria
to be added. The line from Victoria to Beckenham Junction was electrified
on March 3rd 1929, the same day as the short section from Victoria to Elephant
& Castle was added. This left the through trains from Victoria to Coulsdon
North and Sutton as the last left running on the LBSC overhead system. They
last ran in September 1929 with the third rail electric service commencing
from September 22nd.
No sooner was this mass electrification completed when
the Southern Railway saw the potential to extend into outer suburban
territory.
Continue to part two - The spread of the third rail