The British Rail Class 40 is a British Railways diesel-electric locomotive, rated at 2,000 hp and classified as a Type 4. A total of 200 were built by English Electric between 1958 and 1962 and numbered in the series D200-D399. They were for a time the pride of the British Rail early diesel fleet. Despite their initial success, by the time the last examples were entering service they were already being replaced on some top-link duties by more powerful locomotives. As they were slowly relegated from express passenger uses, the type found work on secondary passenger and freight services where they worked for many years. The final locomotives ended regular service in 1985.
Class 40s operated in all areas of British Railways although Western and Southern Region workings were rare. After the early trials the majority of Class 40s were based at depots in northern England, notably Longsight, Carlisle Kingmoor, and Wigan Springs Branch on the Midland Region, and Thornaby and Gateshead on the Eastern Region.
The heyday of the class was in the early 1960s, when they hauled top-link expresses on the West Coast Main Line and in East Anglia. However, the arrival of more powerful diesels such as Class 47 and Class 55, together with the electrification of the West Coast Main Line, meant that the fleet was gradually relegated to more mundane duties. In later life the locomotives were mainly to be found hauling heavy freight and passenger trains in the north of England and Scotland. As more new rolling stock was introduced, their passenger work decreased, partly due to their lack of electric train heating (D255 was fitted with electric train heating for a trial period in the mid-1960s) for newer passenger coaches. They lost their last front-line passenger duties – in Scotland – in 1980, and the last regular use on passenger trains was on the North Wales Coast Line between Holyhead, Crewe and Manchester, along with regular forays across the Pennines on Liverpool to York and Newcastle services.
Throughout the early 1980s Class 40s were common performers on relief, day excursion (adex) and holidaymaker services along with deputisation duties for electric traction, especially on Sundays between Manchester and Birmingham. This resulted in visits to many distant parts of the network. It would be fair to say that few routes in the London Midland and Eastern regions did not see a Class 40 worked passenger service from time to time. Regular destinations included the seaside resorts of Scarborough, Skegness and Cleethorpes on the Eastern region, with Blackpool and Stranraer being regularly visited on the West Coast.