The Class 20 is a small Bo-Bo diesel locomotive produced by BR in the late 1950s and early 1960s. They are sometimes also referred to as the English Electric Type 1. The Class 20 was a freight only diesel design producing 1000 horsepower, ideal for light mixed freight traffic. In total, 228 of the class were built across two production runs. As advancements in diesel traction came thick and fast through the 1970s the locomotives found themselves comparatively weak and relegated to secondary duties.

In service, the locomotives were found to be difficult to drive ‘nose’ first due to what was considered poor visibility for a diesel locomotive, although the visibility was similar to that which would have been seen from a steam locomotive where the long boiler obscured the track ahead. This visibility, combined with their power which became rapidly outclassed by newer locomotives led to class 20s being coupled nose to nose giving it the power and appearance of a standard diesel locomotive, albeit quite a bit longer. As of 2022, 6 locomotives are still in service, 22 are preserved and another handful are in storage with all other examples scrapped.

20189 entered BR service in 1967 as D8189 delivered to a shed in Nottingham. The locomotive would be renumbered under TOPS to 20189 and withdrawn from BR service in September 1990. The locomotive is currently preserved by 20189 Ltd in its original 20/0 condition and is mainline certified. The locomotive is painted in a BR Blue livery with Loram Rail decals, having been one of two of the class to be briefly painted in a Balfour Beatty white and blue livery.

The Class 20 model is fitted with a three pole motor connected to the motor bogie via a driveshaft and worm. Traction tyres give the model extra pulling power and an 8 pin DCC socket allow for digital operation.