British Rail DP1

English Electric DELTIC prototype
DP1 at Harringay station in 1959 in blue livery.
Type and origin Power type Diesel-electric Builder English Electric at Dick, Kerr & Co Works, Preston Serial number EE: 2003 Build date 1955
Specifications Configuration: ​  • UIC Co′Co′ Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Wheel diameter 3 ft 7 in (1,092 mm) Pivot centres 44 ft (13 m) Length: ​  • Over beams 66 ft (20 m) Width 8 ft 9.5 in (2.680 m) Height 12 ft 10.5 in (3.924 m) Loco weight 106 long tons (108 t; 119 short tons) Fuel capacity 800 imp gal (3,600 L; 960 US gal) Prime mover 2 x Napier Deltic E158 D18-12 Engine type opposed piston two-stroke diesel Generator 2 x 1100 kW Traction motors 6 x EE 526/A Cylinders 2 x 18 Transmission Diesel electric Train heating Stone-Vapor/Clarkson steam generator
Performance figures Maximum speed 90 mph (140 km/h) 106 mph (171 km/h) from 1956 Power output 3,300 hp (2,500 kW) Tractive effort 90 mph gearing: 60,000 lbf (266.89 kN) 106 mph gearing: 52,500 lbf (233.53 kN)
Career Operators British Railways Power class Type 5 Numbers DP1 Official name Deltic Retired March 1961 Disposition Preserved at the National Railway Museum Shildon

English Electric DP1, commonly known as Deltic, is a prototype 3,300 hp (2,500 kW) demonstrator locomotive employing two Napier Deltic engines, built by English Electric in 1955.

The high power of the locomotive at an acceptably low axleload resulted in 22 similar locomotives being ordered by British Railways for use on East Coast Main Line express passenger services, the serial production of which became the British Rail Class 55.