The 1955 Modernisation Plan committed British Railways to replacing steam with diesel and electric traction. A pilot scheme was meant to test a small number of designs before large orders were placed, but in practice locomotives were ordered in quantity before the trials were complete, which is why the early diesel fleet held so many different and sometimes unreliable types. By 1960 the first main-line diesels were at work on the East Coast and West Coast routes, and the definitive designs were entering service.
In 1960 diesels were classified by power type, Type 1 (lowest) to Type 5 (highest). The TOPS class numbers used today (Class 20, Class 47, Class 55) were not introduced until 1968. Each class page opens with the type designation and builder name a reader would have found in a period Ian Allan ABC.
The classes
- Class 08, the 350 hp diesel-electric 0-6-0 shunter, the most numerous British locomotive class.
- Class 20, the English Electric Type 1 single-cab freight engine.
- Class 31, the Brush Type 2, later re-engined with English Electric power.
- Class 37, the English Electric Type 3, one of the most durable of all.
- Class 40, the English Electric Type 4, the whistlers of the early main line.
- Class 42 Warship, a Western Region diesel-hydraulic express type.
- Class 45 Peak, the Sulzer Type 4 of the Midland Main Line.
- Class 47, the Brush Type 4, the most numerous main-line diesel.
- Class 52 Western, the Swindon Type 4 diesel-hydraulic.
- Class 55 Deltic, the English Electric Type 5, built for the East Coast Main Line.
More diesel and electric class pages are added as the archive is checked. Hero illustrations on the class pages are labelled editorial illustrations in the house style, not photographs; genuine period photographs replace them as the archive sources them.
- British Transport Commission (1955) Modernisation and Re-Equipment of British Railways.
- Ian Allan ABC of British Railways Locomotives, Combined Volume, diesel section.