Southern Railway 4Sub EMUs (British Rail Class 405): South London suburban electric units

Overview

The Southern Railway (SR) applied the name Sub to a group of electric multiple units that worked short-distance suburban services around South London. These sets were intended for dense, frequent-stop services close to central London and formed an important part of the SR suburban fleet.

Design and formation

Early examples were built as three-car formations. During the 1940s surviving three-car sets were lengthened to four cars by inserting an additional vehicle commonly called an Augmentation trailer. At the same time, some newly built units were produced as four-car sets from the outset. The units were part of the broader family of electric multiple units used on the Southern network.

Service life and classification

These suburban sets remained in passenger service into the early 1980s, with final regular workings ending in late 1983. After nationalisation and the introduction of the TOPS system, the fleet was recorded by British Rail under the TOPS designation Class 405, a number sometimes shortened in everyday use to "4Sub".

Summary

• Originally built as three-car suburban EMUs, later standardized to four cars.
• Additional four-car units were constructed alongside conversions.
• Operated in the South London suburban area until final withdrawal in 1983.
• Listed as Class 405 under the TOPS numbering system administered by British Rail.