On British railways, a Type 4 train refers to a locomotive with a power output between 2,000 and 2,999 horsepower. These powerful machines played a key role in modernising rail travel across the UK. They were crucial in the transition from steam to diesel and paved the way for today’s high-speed trains.

Class 4 locomotives on the British rail network

The story of Class 4 locomotives began with the experimental diesel 10100 and continues with the modernised Class 57s.

10100 - An experimental diesel

The British Rail 10100, also known as ‘The Fell Diesel Locomotive’, debuted in 1950.

British Rail (BR) sought to quickly shift to diesel, but worried that these locomotives would be too heavy for the tracks. The 10100 was built to test solutions.

The 10100 was Britain’s most powerful non-steam locomotive at the time and performed well on inclines. However, it suffered from reliability issues. In 1952, a loose bolt caused severe engine damage which kept it off the rails for a year. BR engineers found it was time-consuming and difficult to maintain.

The 10100 was withdrawn in 1958 and scrapped in 1960. Only one 10100 was ever built.

Class 40

Built by English Electric between 1958 and 1962, the BR Class 40 was a diesel-electric locomotive nicknamed the 'Whistler' because of the turbochargers’ distinctive sound.

Class 40s were mostly used in northern England and on express services for the West Coast Main Line.

Class 40s were sturdy, but they suffered from a variety of maintenance problems. They eventually retired from service in 1985. Today, several Class 40s on display at railway museums and an operational engine is displayed at the East Lancashire Heritage Railway.

Class 41

There were two distinct Class 41s locomotives.

The first Class 41s, built between 1957 and 1958 by the North British Locomotive Company in Glasgow were known as 'Warships’ and were named after Royal Navy vessels like Ark Royal and Cossack. These locomotives were withdrawn 1967 due to design disputes and their non-standard engines.

The second Class 41 trains were prototype High Speed Trains (HST), built in 1972. One set a diesel train speed record of 143mph.Though retired in 1982, they were key to developing the InterCity 125 and later high-speed trains.

Class 42

The Class 42s, introduced in the 1958, were also called 'Warships.' They were lighter and more fuel-efficient than their Class 41 predecessors - ideal for the gradients of the Western Region.

Despite the advances, BR had started to move away from the use of hydraulic transmissions; by 1972 all 42s had disappeared from service. Today, there are two preserved 42s, one at the Severn Valley Railway and the other at the East Lancashire Railway.

Class 43 (Warship)

The diesel-hydraulic Class 43 'Warships' were built between 1960 and 1962. The Class 43s made great express trains, taking passengers quickly and comfortably to the South West. Their powerful engines made journey times much faster.

They remained in service until 1971 and were scrapped the following year when BR phased out the use of hydraulics.

Class 43 HST

Launched in 1975, the Class 43 High Speed Train (HST) revolutionised British rail travel with its speed, comfort, and reliability. These diesel-electric locomotives set a world speed record of  148.5mph for diesel trains.

Many are still in service today, including with Great Western Railway. Others are preserved at various heritage railways across Britain.

Class 44

Built between 1959 and 1960, the Class 44s were among the first large diesels used by BR. Named after the mountains in England and Wales such as Whernside, Cross Fell, and Helvellyn, they helped showcase the potential of diesel power for express passenger travel.

Withdrawn in 1980, they were quickly overtaken by more advanced models.

Class 45

Constructed  between 1960 and 1962, Class 45s were common on the Midland Main Line.

26 of the Class 45s got their names from Royal Marine and British Army regiments. Memorable examples include the 45039 The Manchester Regiment and 45144 Royal Signals.

127 Class 45s were built. The last left service in 1989. Today, there are 12 preserved at heritage railway museums, including Nene Valley and Barrow Hill.

Class 46

Built between 1961 and 1963, Class 46s closely resembled the 45s. Only one Class 46 received a name, this was the 46026, which carried the title Leicestershire and Derbyshire Yeomanry, affectionately known as 'The Lady'.

Three survive in preservation.

 

Class 47

The Brush Type 4 or Class 47 was one of the most iconic diesel-electric trains. Built between 1962 and 1968, over 500 units were produced.

The Class 47s got their names from notable individuals and organisations, including Isambard Kingdom Brunel and Florence Nightingale.

The Class 47s remained in service for decades.

Class 48

A small batch of Class 48s were essentially experimental versions of the 47, fitted with different sized engines (Sulver V12s). BR wanted to test the performance of the newer engine compared to the old.

BR eventually replaced the engines with the standard Class 47 power unit, reclassifying the locomotives accordingly.

Class 50

Built between 1967 and 1968 the BR Class 50 locomotive was nicknamed 'Hoovers' for the sound its cooling fans made.

Class 50s were used mainly on the West Coast Main Line on services  between Crewe and destinations like Preston, Glasgow, and Aberdeen. They were later refurbished and transferred to the Western Region.

50 Class 50s worked across the UK until their eventual retirement in 1994. Several are preserved today at locations such as the South Devon Railway and Mid-Norfolk Railway.

Class 52

The BR Class 52, better known as ‘Westerns’, were diesel-hydraulic locomotives introduced between 1961 and 1964.

The Class 52 Westerns were popular but short-lived, as BR phased out hydraulic systems in favour of diesel-electric. Eventually, Class 50s and high-speed trains replaced the 52s.

You can find seven preserved 52s at heritage railways, including Severn Valley, and Didcot.

Class 53

The Class 53 ‘Falcon’ was a one-of-a-kind prototype diesel-electric locomotive built in 1961 by Brush Traction.

Although technically successful, it was rendered obsolete by new, more powerful single-engine models. The Falcon left service in 1975 and BR did not preserve it.

Class 57

Between 1998 and 2004, BR refurbished Class 47s into modern Class 57s using EMD engines and re-conditioned alternators.

They subclasses were created:

• 57/0: This 1998 train was for freight traffic only.
• 57/3: Virgin Trains intended this 2002 loco for passenger services.
• 57/6: These engines were for Great Western Railway's (GWR) Night Riviera sleeper service; these still continue to operate today.

Travel with Avanti West Coast

The tradition of innovation that began with Britain’s early diesel locomotives continues today with modern high-speed trains.

Experience this legacy firsthand by travelling on Avanti’s leading Evero and Pendolino trains. These trains carry forward the same spirit of performance and progress that defined the Type 4 era.