The Southern Railway gave the designation 4-LAV to the electric multiple unit

Electric multiple unit

An electric multiple unit or EMU is a multiple unit train consisting of self-propelled carriages, using electricity as the motive power. An EMU requires no separate locomotive, as electric traction motors are incorporated within one or a number of the carriages...

s built to work the semi-fast services on the route between London and Brighton. None of these units survived long enough in British Rail

British Rail

British Railways , which from 1965 traded as British Rail, was the operator of most of the rail transport in Great Britain between 1948 and 1997. It was formed from the nationalisation of the "Big Four" British railway companies and lasted until the gradual privatisation of British Rail, in stages...

 ownership to be allocated a TOPS

TOPS

Total Operations Processing System, or TOPS, is a computer system for managing the locomotives and rolling stock owned by a rail system...

 class.

Construction

The original series of 4-LAV (4-car Lavatory stock) units, (numbers 1921–1953), were built at Eastleigh carriage works

Eastleigh Works

Eastleigh Works is a locomotive, carriage and wagon building and repair facility in the town of Eastleigh in the county of Hampshire in England.-History under the LSWR:...

 during 1931 and 1932 for use on the newly electrified London to Brighton line

Brighton Main Line

The Brighton Main Line is a British railway line from London Victoria and London Bridge to Brighton. It is about 50 miles long, and is electrified throughout. Trains are operated by Southern, First Capital Connect, and Gatwick Express, now part of Southern.-Original proposals:There were no fewer...

. They were fitted with four Metropolitan-Vickers

Metropolitan-Vickers

Metropolitan-Vickers, Metrovick, or Metrovicks, was a British heavy electrical engineering company of the early-to-mid 20th century formerly known as British Westinghouse. Highly diversified, they were particularly well known for their industrial electrical equipment such as generators, steam...

 275 h.p. traction motors. Despite the prominence given to the lavatory provision in the SR designation, there was actually only one lavatory in the whole four-car unit, and due to the lack of corridors in the unit, only passengers in that coach had access to it. The units were renumbered 2921–2953 in the January/February 1937 renumbering of SR EMUs.

Two further units, (numbers 2954 and 2955) were added to stock in 1940, under the direction of Oliver Bulleid

Oliver Bulleid

Oliver Vaughan Snell Bulleid was a British railway and mechanical engineer best known as the Chief Mechanical Engineer of the Southern Railway between 1937 and the 1948 nationalisation, developing many well-known locomotives.- Early life and Great Northern Railway :He was born in Invercargill,...

. These were fitted with English Electric

English Electric

English Electric was a British industrial manufacturer. Founded in 1918, it initially specialised in industrial electric motors and transformers...

 275 h.p. traction motors.

The DMBT (Driving Motor Brake Third) had a full-width cab with a guard's compartment behind, and seven third class compartments seating 70. The TC (Trailer Composite) had five first-class and four third-class compartments seating 40 in each class. The TCL (Trailer Composite with Lavatory) had five first-class and three third-class compartments seating 30 and 24, respectively, with a toilet at each end.

One unit, number 2926, was fitted with one 2-HAL

British Rail Class 402

The Southern Railway gave the designation 2-HAL to the electric multiple units built during the late 1930s to work long-distance semi-fast services on the newly electrified lines from London to Maidstone and Gillingham...

 type motor coach.

Use

Throughout their careers they operated the slower services on the London to Brighton line

Brighton Main Line

The Brighton Main Line is a British railway line from London Victoria and London Bridge to Brighton. It is about 50 miles long, and is electrified throughout. Trains are operated by Southern, First Capital Connect, and Gatwick Express, now part of Southern.-Original proposals:There were no fewer...

 between either London Bridge or Victoria and Brighton railway station

Brighton railway station

Brighton railway station is the principal railway station in the city of Brighton and Hove, on the south coast of England. The station master is Mark Epsom...

. They were also used on stopping trains on the Arun Valley Line

Arun Valley Line

The Arun Valley Line, also known as the Mid Sussex Line, is part of the Southern-operated railway services. For the initial part of the route trains follow the Brighton Main Line, and at a junction south of Three Bridges the route turns westwards...

 and on the Sussex coast lines to the east

East Coastway Line

East Coastway is the name used by the train operating company, Southern , for the routes it operates along the south coast of Sussex and Kent to the east of Brighton, England. Those to the West of Brighton are named the West Coastway Line...

 and west

West Coastway Line

The West Coastway Line is a railway line in England, along the south coast of West Sussex and Hampshire, between Brighton and Southampton, plus the short branches to Littlehampton and Bognor Regis....

of Brighton.

Formations

Initial formations of these units were as follows (cars not always formed in numerical order):

Unit Numbers
1921–1953 / 2921–2953	10501–10565 (odds)	12001–12033	11501–11533	10502–10566 (evens)
2954–2955	10497–10499	11999–12000	11534–11535	10498–10500

Withdrawal

The majority of the 4-LAV units were withdrawn from ordinary passenger service in 1968, with the final few going in April 1969. Almost all the units were scrapped, but some of the 1940-built cars survived in departmental (non-revenue earning) use for several more years. However, no 4-LAV stock exists today.