British Rail Class 421
class of 4-car EMU, (4-BIG, 4-CIG) bought for Brighton Line electrification
The British Rail Class 421 (4-CIG) electric multiple units were built at British Rail's Holgate Road carriage works in York, England, between 1964 and 1972. The trains were built in two batches and were initially introduced on services on the Brighton Main Line; later, they were introduced on services to Portsmouth. They replaced older Southern Railway-designed trains, such as the 5-BEL Brighton Belle and 4-COR. The fleet's lifespan was 46 years.
Design
Standard fleet
These contained only passenger accommodation and formed the bulk of the fleet. They were unusual in that all four traction motors were mounted on one non-driving motor coach. Trains consisted of two driving trailers, sandwiching the non-driving motor coach and an intermediate trailer.
Trains were built in two batches: 'Phase 1' units were built from 1963 to 1966 for the Brighton Line and were numbered 7301-36; these were followed in 1970-72 by the 'Phase 2' units, built primarily for the Portsmouth Direct line, numbered 7337-438.
4-BIG fleet
The 4-BIGs were similar to the class standard, but contained a buffet car in place of the intermediate trailer. They were also built in two batches: 'Phase 1' trains were built in 1965/66 and were numbered 7031-48; 'phase 2s' were built in 1970 and were numbered 7049-58.
The 4-BIG fleet were initially classified as Class 420 by British Rail, under the TOPS system introduced in 1968, and then Class 422.
Begin with the source’s own compact description: “British Rail Class 421” is class of 4-car EMU, (4-BIG, 4-CIG) bought for Brighton Line electrification. The dossier treats that line as a proposition to test through British, Rail and Class, not as a finished interpretation.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 11, 2026. The linked authority identifier is Q3303603. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1964, 1972, 1963 and 1966.
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This entry incorporates text from “British Rail Class 421” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.