Based on the diesel shunting locomotives of the LMS, which later became the class 11, the class 08 was created as the standard shunting locomotive for British Railways. Power was provided by a six-cylinder from English Electric via two electric traction motors and coupling rods. 996 units were built in about ten years, making the class 08 the most-built British diesel locomotive. The classes 09, 10 and 13 were also created on this basis. Around 100 class 08 locomotives are still in commercial use today and more than 80 are preserved today, many of them operational.

The Class 20, officially known as the English Electric Type 1, was the first mass-produced British mainline diesel locomotive. It was at the top end of power class 1 with a maximum of 1,000 hp and was intended for lighter operation with mixed freight trains. Thus, it did not receive a train heating boiler and the power was drawn from the eight-cylinder version of the English Electric diesel engine. The engine code 8SVT indicated a supercharged V8 engine. Its distinct sound led to the nickname “Chopper”.

Unusual for British locomotives, only one cab was installed at one end of the locomotive, with one driver's desk for each direction. Since the transition from steam to diesel was just beginning at the time, the poor visibility in one direction was manageable. Due to the previously developed diesel locomotives in this power class not being a success, 128 were ordered, which were delivered between 1957 and 1962.

As planned, the locomotives were primarily used for freight traffic and were usually running cab-first. In the summer they were also used as reinforcements in passenger traffic, and their duties also included shunting empty passenger trains. The lighting system initially consisted of the multitude of lamps to form combinations for identifying the type of train, as was common on British steam locomotives. From 1960 these were replaced by the large boxes for displaying the head codes.

A further 100 were built between 1965 and 1968, bringing the total to 228. Some came with slow-speed control for loading and unloading coal trains. When the light mixed freight trains became fewer and fewer due to the growing road traffic and light mainline locomotives were no longer needed, the locomotives were increasingly seen in pairs in front of heavier trains. They were coupled together with the cabs on the outside to allow sufficient visibility in both directions. Some of the coal trains in the Scottish lowlands were even operated with three locomotives.

At the end of the British Rail era, they were rarely found on main lines in front of regular trains. After privatization, the class 20 was increasingly used by its new operators for special tasks. Some were used on construction trains, helping to build the Eurotunnel and the High Speed 1 line from London to the Eurotunnel. Some were even used temporarily in France for this task. Direct Rail Services operated nuclear flask trains with one locomotive at each end. The DRS “Railhead Treatment Trains” also had a locomotive at each end, which used high pressure to clear the tracks of leaves in autumn at high speed. Class 20 locomotives have not been used in this role since 2020. At that time, the number of locomotives in general had shrunk considerably, also the delivery services of the new S-stock cars for the London Underground were already history by this time. 22 are preserved for posterity. They are all operational, either only for individual heritage lines or with main line certification.

The class 22, also called North British Type 2, was a diesel-hydraulic locomotive built for BR's Western Region between 1958 and 1962. It was technically closely related with the class 41 “Warship”, but had only one engine and gearbox and was thus called “Baby Warship”. The MAN V12 engine delivered 1,000 hp in the first six locomotives and 1,100 in the following 52. On the outside, these locomotives looked similar to the diesel-electric class 21.

They were introduced into service in 1959 and in the first years, North British had to remedy some teething problems. After this, they had an availability of around 85 percent. But while production was still running, new diesel-hydraulics with much more power were built and displaced the class 22 into secondary duties. They were withdrawn between 1967 and 1972.

The diesel locomotives later called class 24 were designed as a part of the 1955 modernisation program and initially carried numbers starting with D5000. Their second name “Sulzer Type 2” gives reference to the origin of the diesel engine and the power class. One requirement was that as many parts as possible could be taken off the shelf from the industry.

The engine of type 6LDA28 was a direct-injected and turbocharged six-cylinder that was the same as in the CIÉ class 101, but with an increased output of 1,160 hp. Other parts like the generator, traction motors, brakes, multiple working equipment and steam heating boiler were also taken from existing types. On the cab ends they had gangway doors, but as in other locomotives they were rarely used and later got sealed.

Some belonged to the lighter subclass 24/1. These had smaller fuel and water tanks to increase their route availability in the Scottish highlands. Most class 24/0 and 24/1 locomotives later lost their steam heating boiler when they were no longer used in passenger service. They were withdrawn between 1973 and 1980. Today, four are being preserved with all of them again carrying their pre-TOPS numbers.