The British Rail Class 411 (4CEP) electric multiple units were built at Eastleigh works from 1956–63 for the newly electrified main lines in Kent. These units, which used a British Railways Mark 1 bodyshell, were based on the earlier Southern Railway 4 COR design, built in 1937. Variants of the class 411 design included the class 410 and class 412 4 BEP units, which contained a buffet car in place of a standard trailer. They were later used on services in Sussex and Hampshire; following the privatisation of British Rail in 1995, the units were used by the Connex South Central, Connex South Eastern and South West Trains franchises.

In early 1999, five units were converted to Class 411/9 3CEP units, with the removal of the second-class open trailer. These removed trailers had not had so much work carried out on them at the time of refurbishment (as they were basically unchanged apart from cosmetic appearance and installation of hopper windows) and many had become severely corroded. This was necessary, as some stations could only accommodate 11 carriages. A further 13 units were later converted. The 3 CEP units were renumbered into the series 1101–1118.

The fleet's lifespan was 49 years, these units are the longest-lived BR Mark 1 EMUs. Four complete units have been saved for preservation.