British Railways DP1

The nose end of DP1 at Locomotion

The prototype Deltic was a demonstrator locomotive built by English Electric in 1955. This locomotive resulted in 22 similar locomotives being ordered by British Railways, which became their Class 55.


The English Electric company, which had absorbed the engine maker Napier & Son into its vast empire, was (among many interests) a major builder of diesel and electric locomotives. EE saw the potential of Napier's Deltic engine for rail traction and in 1955 built a demonstrator at its Dick, Kerr works in Preston. Officially numbered DP1 (Diesel Prototype number 1), although this was never borne on the locomotive, it carried the word DELTIC in large white letters on its powder-blue sides. Plans to name the locomotive "Enterprise" never came to fruition and it was to be known to all just as "Deltic".

Long cream stripes were painted on the sides, a visual device to make the locomotive's high sides appear more slender and speedier; three curved chevrons in the same creamy white on the noses gave it the impression of speed. The locomotive's styling was reminiscent of American locomotives (partly because English Electric initially planned to offer the type for export) with high noses and small, somewhat swept-back cab windows set back behind them; to add to the American look of the locomotive to British eyes, a large headlight was fitted to each nose (these lights were never installed but would have been of the rotating 'beacon' type as fitted to North American locomotives of the era). Two 18-cylinder Deltic engines were fitted, derated from the 3,100 horsepower (2.3 MW) of the marine engines to 1,650 horsepower (1.2 MW) each, 3,300 horsepower (2.5 MW) total. This derating reduced the stress on the engines, thereby increasing the service life and length of time between overhauls.

Service with British Railways

The locomotive first saw service on the London Midland Region of British Railways but the intention soon became to electrify the major routes on that Region. On the Eastern Region, however, no diesel replacement of conventional design seemed to be available for Gresley's swift and powerful Pacifics, particularly the A4. Only the Deltic appeared to offer the power and speed required within the restraints of sensible axle load, and it was soon running on that Region.


In 1961 "DELTIC" was withdrawn after a serious powerplant failure; by that time the production Class 55 locomotives were coming into service. Plans to test it in Canada fell through and the locomotive was donated to the Science Museum, London. It is now in the National Railway Museum site Locomotion in Shildon, County Durham, England.