A History of the British Rail Class 20 Diesel Locomotive

In the mid 1950s British Rail published its’ "Modernisation Plan”. This plan was intended to bring the railway system into the 20th century and included a large-scale dieselisation programme to replace the existing steam locomotive fleet.

The British Railways board went about this by ordering small batches of prototype locomotives from different manufacturers that could be tested in real world conditions to see which performed the best.

The anticipated diesel locomotive fleet was divided up into five different power brackets, with Type 1 was the least powerful and the Type 5s the most powerful.

The Type 1s were intended to work small scale freight trains of the kind you would find on local branch lines.

There were a number of contenders vying for the Type 1 BR contract. English Electric put forward its Type 1 which would later become the Class 20.

British Thomson-Houston created the BTH Type 1, later classified as Class 15 and North British Locomotive Company’s version was the North British Type 1 which would become the Class 16.

The English Electric locomotive was by far the most successful of the three contenders. Both the Class 15 and 16 suffering from poor reliability and design issues.

Although the Class 20 seemed like the obvious choice for the primary British Rail Type 1 locomotive in 1962 BR ordered 117 locomotives from the Clayton Equipment Company known as the Clayton Type 1, later designated as the Class 17. This was despite the fact that no prototype and been build or tested it so was a completely unproved design.

This decision proved disastrous as they quickly acquired a reputation for unreliability largely due to the engines, which continued to deliver poor performance even after extensive modifications. All of the class had been withdrawn by 1971.

Due to the poor performance of the other Type 1s a total of 228 Class 20 locomotives would go on to be built by English Electric between 1957 and 1968 and became the standard Type 1 British Rail locomotive.


During their lifetime as the freight work they were designed for dried up they increasingly worked in pairs, coupled nose to nose for greater driver visibility. They could then be used to work heavier freight trains such as MGR coal workings.

They could also be seen working in top and tail mode as seen here on this weed killing train.

The reliability and versatility of the class meant that many locomotives survived into the privatisation era and examples of can still be found working on the UK mainline to this day.

I late 1994 Direct Rail Services was created as a wholly owned subsidiary of British Nuclear Fuels Ltd. The primary purpose of DRS was to take over the rail-based handling of nuclear material from British Rail after privatisation.

DRS would go on to acquire 21 Class 20s.

A number of them were overhauled at Brush Traction in Loughborough and were renumbered as Class 20/3 in the range 20301 to 20315.

They were used to work a variety of nuclear flask trains around the country as well the seasonal rail head treatment trains during the Autumn leaf fall season.

In the early 2000s a number of preserved Class 20s were used during the construction of the Channel Tunnel Rail Link high speed line through Kent, later renamed as High Speed 1.

In the following clips filmed between 2010 and 2025 we will look at the class in action on the UK mainline.