British Rail Class 55

British Rail Class 55
D9009 Alycidon at the National Railway Museum, York
Type and origin Power type Diesel-electric Builder English Electric at Vulcan Foundry Build date 1961–1962 Total produced 22
Specifications Configuration: ​  • Whyte Co-Co  • UIC Co'Co' Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Wheel diameter 3 ft 9 in (1.143 m) Wheelbase 58 ft 6 in (17.83 m) Length 69 ft 6 in (21.18 m) Width 8 ft 9+1⁄2 in (2.68 m) Height 12 ft 10 in (3.91 m) Loco weight 99 long tons (101 t) Fuel capacity 900 imp gal (4,100 L; 1,100 US gal) Prime mover Napier Deltic D18-25, 2 off MU working Not fitted Train heating Steam generator; later Electric Train Heating Train brakes Vacuum; later Dual (Air & Vacuum)
Performance figures Top speed 100 mph (161 km/h) Power output Engines: 1,650 bhp (1,230 kW) × 2 Tractive effort Maximum: 50,000 lbf (222 kN)
Career Railroad(s) British Railways Number D9000–D9021; later 55001–55022 Nicknames ‘Deltics’ Axle load class Route availability 5

The British Rail Class 55 is a class of diesel locomotive built between 1961 and 1962 by English Electric. They were designed for the high-speed express passenger services on the East Coast Main Line between London King's Cross and Edinburgh. They gained the name "Deltic" from the prototype locomotive, DP1 Deltic, which in turn was named for its Napier Deltic power units. 22 locomotives were built, and they dominated services on the line until their withdrawal at the end of 1981. Six locomotives were preserved and are still running today.