Class 55 (English Electric 3,300hp Diesel-Electric "Deltic")

In the early days of British Rail dieselisation the largest locomotives were known as the Type C with over 2,000hp. However it was soon clear that more powerful locomotives would be needed for the principal expresses and heaviest freight though none existed at the time - until the arrival of English Electric's incredible Deltic prototype in 1955 with 2 innovative Napier Deltic engines and 3,300hp to play with. BR revised its power classifications to the now familiar Types 1 to 5 with the Type 5 for locomotives over 3, 000hp [1].

With high power and a relatively low weight (the Deltic was 32 tons lighter than a Class 45 but brought 800hp more to the table) the Deltic proved itself on top BR expresses and a production order for 22 was made to replace ex-LNER Pacifics on the East Coast Main Line [2]. The production Deltics differed in appearance to the prototype and construction, one problem with the prototype had been its awkward size which limited its route availability, the production Deltics were somewhat slimmer and a bit longer [3].

Number built: 22
Built: 1961-62
Builder: English Electric Vulcan Foundry
Engine: 2 Napier Deltic 18-25 diesels
Power: 3, 300 hp (2, 460 kW)
Wheel arrangement: Co-Co

The Class 55s as they became known performed admirably on the ECML until being replaced by the High Speed Train in the late 1970s with a final withdrawal from service at the end of 1981. Although they still had a lot to offer the Class 55s were expensive to maintain and the small fleet made them uneconomic. Six Class 55s were preserved as well as the prototype, the diesels (along with the Western Class 52s) attracting a level of popularity and interest not seen since the end of steam.

This wasn't the end of the Deltic story however, in the mid-1990s the Class 55s made a return to National Rail service with 4 being mainline certified [4] and are often used for charter services and spot hire, even hauling freights.
D9002 at Kidderminster SVR

55 019 at Kidderminster SVR

55 019 at Bewdley

D9002 again

55 019 approaches a train

Side view of D9002

[1] Brian Haresnape, Early Prototype and Pilot-Scheme Diesel Electrics (Ian Allan, 1981) p. 11
[2] Haresnape, Prototypes p. 31
[3] Brian Haresnape, Production Diesel Electrics Types 4 and 5 (Ian Allan, 1984) p. 42
[4] Colin J. Marsden, Traction Recognition (Second Edition) (Ian Allan, 2008) p. 48