55011

55011 refers to a specific instance of a British Rail Class 55 locomotive, often colloquially known as the "Deltic" class. These locomotives were built by English Electric at their Vulcan Foundry works between 1961 and 1962 for British Railways. The Class 55 was a powerful diesel-electric locomotive designed for express passenger service on the East Coast Main Line.

The locomotive designated 55011 was named "Royal Northumberland Fusiliers". This naming convention was applied to all locomotives in the Class 55, with each being named after a famous racehorse. However, 55011 was an exception to this naming convention, being named after a regiment of the British Army. The Deltic locomotives were instantly recognizable by their distinctive sound, produced by their Napier Deltic engines, which were two-stroke diesel engines comprising three Napier 18-cylinder engines arranged in a triangular configuration.

These locomotives were originally intended to haul trains at speeds up to 100 miles per hour. They were a significant step forward in British railway technology at the time, providing high power and reliability. 55011, like its sister locomotives, operated primarily on the busy route between London King's Cross and Edinburgh Waverley. The Deltics were eventually withdrawn from service between 1980 and 1982, being replaced by more modern diesel and electric traction. Despite their relatively short operational life, they remain highly regarded by railway enthusiasts and several have been preserved.