The class 3SUB were DC suburban electric multiple units, introduced by the London and South Western Railway in 1915.

[1] The lines were electrified at 6.7 kV 25 Hz AC, using overhead supply.

[2] The London and South Western Railway (LSWR) electrified its lines on the third rail DC system.

[1] In 1922, the South Eastern and Chatham Railway (SECR) sought permission to electrify certain lines in London.

On 1 January 1923, the LSBC, LSWR and SECR were merged into the Southern Railway (SR).

[3] Eighty-four electric multiple units, numbered E1–E84, were constructed in 1913 by converting steam-hauled carriages which had been built from 1904 for suburban service.

[7] The SR renumbered the electric multiple units 1201-84 and the trailer sets 1001-24.

[8] In 1933, eight units were transferred to Brighton to work local services to Worthing.

[9] A total of 51 suburban electric vehicles were destroyed by enemy action during WWII.

[10] Two-coach trailer sets converted in 1925 from ex-LBSC nine-compartment bogie third carriages.

[9] Two-coach trailer sets converted in 1925 from ex-LBSC nine-compartment bogie third carriages.

[12] Two-coach trailer sets converted in 1928 for use on Eastern Section services.

[9] Three-coach units built new in 1925 for Waterloo to Guildford via Cobham services.

Electric motors were by Dick, Kerr & Co. Ltd., rated at 300 horsepower (220 kW).

Electric motors were by Dick, Kerr & Co. Ltd., rated at 300 horsepower (220 kW).

[15] Three-coach units converted in 1937 from ex-LSWR bogie carriages.

[16] Three-coach units converted in 1928 from ex-LBSC bogie carriages.

[16] Three-coach units converted in 1928 from ex-LBSC bogie carriages.

[16] Three-coach units converted in 1930 from ex-LBSC bogie carriages.

They were 256 feet 9 inches (78.26 m) long, weighed 139 tons and seated 353 people.

They were 257 feet 5 inches (78.46 m) long, weighed 139 tons and seated 350 people.

They were 245 feet 0 inches (74.68 m) long, weighed 133 tons and seated 350 people.

They were 257 feet 5 inches (78.46 m) long, weighed 137 tons and seated 370 people.

It reverted to three carriages and entered departmental service as an instruction unit, numbered S10S.

[21] Fifty-one suburban electric carriages were destroyed by enemy action during WWII.