British Rail Class 508

The BR Class 508 was a fleet of forty-three three-car 750 V DC electric multiple unit sets built at BREL York between 1979 and 1980, ordered alongside the Class 507 for the Merseyrail network but with a more complex operational history that saw a significant portion of the fleet transferred away from Merseyside and redeployed on the Southern Region before eventually returning to Liverpool.

The Class 508 used the same basic body and mechanical specification as the Class 507 but was delivered in larger numbers and with a slightly different vehicle composition: where the 507 used a DMBS–TS–DMS formation, the 508 was built as DMBS–TS–DTBS, the final vehicle being a Driving Trailer Brake Standard rather than a powered motor car. This meant the Class 508 had only one powered motor coach in the three-car set compared to the Class 507's two, giving lower power output but a simpler and lighter formation.

After delivery to Merseyrail in 1979–80, it became apparent that the network did not require the full forty-three sets immediately, and BR transferred twenty-five Class 508 sets to the Southern Region, where they worked South London DC third-rail services from Waterloo and Victoria. These sets were allocated to Wimbledon depot and worked alongside Class 455 and Class 415 stock on inner-suburban duties for several years during the early 1980s. This unusual inter-regional transfer of a fleet ordered for one specific network to work on an entirely different one reflected the operational flexibility of the standardised BREL design.

By the early 1990s, the Southern Region sets were returned to Merseyrail as the Merseyside network's passenger growth required more capacity. The complete Class 508 fleet was reunited on Merseyside and, like the Class 507, underwent comprehensive refurbishment to extend their service lives. As of 2026, the Class 508 fleet continues in Merseyrail service alongside the remaining Class 507s, with the Stadler Class 777 Metro trains progressively replacing both classes as deliveries continue.