The British Rail Class 202 (or 6L) diesel-electric multiple units were built from 1957-58 at Eastleigh and Ashford Works. These units were built to work the London Charing Cross to Hastings services. Several tunnels along the route had restricted clearance, meaning that these units were built with a narrow body profile. Similar to the Class 201 (or 6S) they were built to the longer (63ft 5in) BR Mk1 standard and therefore had 288 seats (240 second class plus 48 first class) compared to the 242 (200 42) of the 6S units.

The last six-car units were withdrawn in 1986, when the Hastings line was electrified. The line through the tunnels was reduced to single track, allowing standard loading gauge Class 411 electrical multiple units to replace the diesel units on passenger services. One unit was subsequently reinstated to provide emergency cover, and was renumbered as 202001 to conform with the TOPS numbering system.

After the mass withdrawals of 1986, several units were reformed as four-car units, and subsequently renumbered into the Class 203 series. In addition, several vehicles saw further use as departmental vehicles. One complete unit, and 2 individual vehicles have been preserved.