The Class 55, universally known as the Deltic, was the most powerful single-unit diesel locomotive in the world when it entered service, and it was built for one job: to replace the Gresley and Peppercorn Pacifics on the fastest East Coast Main Line expresses. Only twenty-two were built, yet they held the crack Kings Cross to Edinburgh trains for the best part of two decades.
The prototype
The production class was preceded by a single English Electric prototype, named DELTIC, which the company built at its own expense in 1955 and lent to British Railways for trials. Its performance on the West Coast and then the East Coast persuaded British Railways to order a production fleet. The prototype is preserved and is now held in the national collections.
Design and build
The twenty-two production locomotives were built by English Electric in 1961 and 1962. Each was powered by two Napier Deltic engines, an unusual opposed-piston design in a triangular layout that gave the class both its name and its very high power-to-weight ratio. The locomotives were numbered in the D9000 series and named after regiments associated with the areas they served and after famous racehorses, a nod to the East Coast racing tradition.
In service
From 1961 the Deltics took over the principal East Coast expresses between Kings Cross, Leeds, Newcastle, and Edinburgh, displacing the Pacifics that had held them since the 1930s. Their high availability let twenty-two locomotives do the work of a far larger steam fleet, and they accelerated the East Coast timetable markedly. They were displaced from top-link work only by the High Speed Train in the later 1970s.
Withdrawal and preservation
The class was withdrawn at the beginning of the 1980s. Because of the affection in which they were held, an unusually high proportion survived: six of the twenty-two production locomotives are preserved, alongside the original prototype. Several have run on the main line in preservation. See the preserved railways directory for current locations.
- Ian Allan ABC of British Railways Locomotives, diesel section, for the D9000 numbering and names.
- National Railway Museum, for the record of the prototype DELTIC and 55002 in the national collections.
- Standard English Electric Deltic class histories.