British Rail Class 85

Design and characteristics

Class 85s are four-axle electric locomotives designed for overhead 25 kV AC operation. Early machines were fitted with germanium-based rectifiers to convert alternating current for the traction motors; these were subsequently replaced by more robust silicon rectifiers. The class combined then-modern electrical components with British Rail engineering practices of the era and was intended to provide reliable passenger and freight haulage on newly electrified routes.

• Builder: Doncaster Works
• Production: 40 locomotives, 1961–1964
• Electrical system: 25 kV AC overhead
• Rectifiers: originally germanium, later silicon
• Wheel arrangement: four driven axles (Bo‑Bo / 4‑axle)

History and numbering

Under the early departmental code system the design was classified AL5 (the fifth 25 kV AC locomotive type) and the individual locomotives were initially numbered E3056–E3095. With the introduction of the TOPS computerised numbering system, they were reclassified as Class 85 and renumbered into the 85001–85040 series. During their working lives some members received further sub-classification and modifications to suit particular duties.

Operations and modifications

Class 85s entered traffic as electrification extended along the West Coast Main Line, working services to and from London Euston and into the industrial northwest. Typical destinations and depots served included Birmingham, Crewe, Liverpool, and Preston. By 1965 electrification had reached London Euston, enabling through electric services between the capital and these cities via the West Coast Main Line.

A subset of the class was adapted for freight work and reclassified internally as the 85/1 series; these locomotives were restricted to an 80 mph maximum speed for their intended heavy freight duties. Mechanical and electrical upgrades during their careers aimed to improve reliability and to keep the fleet compatible with evolving signalling and train formation requirements.

Legacy and significance

The Class 85s played an important role in the early era of AC mainline electrification in Britain. Their service helped validate equipment choices and operational practices that informed later standard classes. While progressively superseded by newer designs with higher performance and simplified maintenance regimes, Class 85s illustrated the transition from experimental prototypes to the standardised electric traction that dominated British intercity routes in the late 20th century.

For further technical detail and preserved examples, consult specialised sources and heritage group publications that document the technical modifications and individual histories of the locomotives from this pioneering class.

More on Class 85 | Germanium rectifiers | Silicon rectifiers | West Coast Main Line | Birmingham | Crewe | Liverpool | Preston