The British Rail Class 56 is a type of diesel locomotive designed for heavy freight work. It is a Type 5 locomotive, with a Ruston-Paxman power unit developing 3,250 bhp (2,423 kW), and has a Co-Co wheel arrangement. The fleet was introduced between 1976 and 1984. The first thirty locomotives (Nos.56001-56030) were built by Electroputere in Romania, but these suffered from poor construction standards and many were withdrawn from service early. The remaining 105 locomotives were built by BREL at Doncaster Works (nos. 56031 to 56115) and Crewe Works (Nos.56116 to 56135). Enthusiasts nicknamed them "Gridirons" (or "Grids" for short), due to the grid-like horn cover on the locomotive's cab ends.