British Rail Class 70 (Southern Railway 3rd‑rail electric locomotives)

Design and construction

These locomotives used a Co‑Co wheel arrangement and were designed to operate from the Southern Railway's third‑rail DC electrification system (750 V DC). The mechanical bodies were produced at Ashford Works and the electrical equipment was the work of staff electrical engineers. The styling and structural details reflected the influence of Southern Railway engineering practices of the period.

• Wheel arrangement: Co‑Co (six axles, all powered).
• Current collection: third‑rail DC suitable for the Southern network.
• Builders: Southern Railway at Ashford and later British Railways construction.
• Key designers: the electrical systems were led by Alfred Raworth with body work by Oliver Bulleid; subsequent modifications were carried out by C. M. Cock.

History and numbering

The first two examples were constructed at Ashford in 1941 and 1945 and were initially identified by the Southern Railway as CC1 and CC2. A third locomotive was completed under British Railways control in 1948; this example carried the number 20003. CC2 incorporated alterations introduced after a change in the electrical engineering leadership. Because only three were built, they never formed a large class and remained largely experimental.

During their working lives these locomotives were employed on duties appropriate to heavy electric traction on the Southern Region. Their limited number and the pace of post‑war standardisation meant that their influence was more technical than widespread: components and ideas tested on the trio informed later designs rather than spawning a large family of identical machines.

Significance and distinctions

Although called Class 70 in some historical records, these 1940s locomotives are not related to the modern diesel‑electric Class 70 locomotives introduced decades later; the shared designation reflects changes in numbering and classification systems over time rather than technical continuity. The small Southern Class 70s are chiefly of interest to students of electrification, Southern Railway practice, and transitional post‑war British railway engineering.

For further technical details and historical context see contemporary engineering reports and specialised histories of Southern Railway electrification: technical summary, Southern Railway background, Ashford Works and biographical notes on the designers.