The English Electric Company of Great Britain capitalised on the potential for orders resulting from the British Railways (BR) 1955 Modernisation Plan to rid the UK of steam locomotives. In the following years it produced some of the most iconic and successful diesel locomotives.

The 200 Class 40 locomotives, built between 1958-1962, were once the pride of the early national diesel fleet. They were amongst some of the first diesels built for BR as part of its Modernisation Plan. The majority of the class were built at the Vulcan Foundry, Newton-le-Willows. One batch of twenty locomotives were built at the Robert Stephenson and Hawthorn factory in Darlington to allow capacity at the Vulcan Foundry for the manufacture of the production Deltic locomotives. Seven examples remain in existence.

The 50 Class 50 locomotives, built between 1967-1968, were the last dedicated mixed-traffic locomotive built in the UK. Upon their introduction they were used on the West Coast Main Line (WCML) to improve passenger timings on the then non-electrified portion up to Glasgow. Eighteen examples remain in existence.

The 22 Class 55 (Deltic) locomotives, built between 1961-1962, were perhaps the most iconic diesel locomotives ever to run on the national network. They were designed for high-speed express passenger services on the East Coast Main Line (ECML) between London King's Cross and Edinburgh. They gained the name from the DP1 DELTIC prototype locomotive which had been named after its twin Napier Deltic power units. At the time they were built they were the most powerful single-unit diesel locomotives in the world and transformed services on the line until their withdrawal in 1982. Six examples remain in existence.
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