British Rail Class 503 trains were 70mph (110km/h) electric multiple units. They were introduced in two batches — in 1938 by the London, Midland and Scottish Railway (LMS) with a further batch (built to a similar design) in 1956 by the then nationalised British Railways (BR).
| British Rail Class 503 | |
|---|---|
 A British Rail Class 503 train on the Liverpool Loop and Link underground system. This train was one of the original batch built by the LMS in 1938. | |
| Specifications | |
| Car length | 58ft 0in |
