The British Rail Class 55, also known as a Deltic, or English Electric type 5, is a class of diesel locomotive built in 1961 and 1962 by English Electric for British Railways. They were designed for the high-speed express passenger services on the East Coast Main Line (ECML) between Edinburgh and London King's Cross. They gained the name "Deltic" from the prototype locomotive, DP1 Deltic (the running number DP1 was never carried), which in turn was named after its Napier Deltic power units. At the time of their introduction into service, the Class 55s were the most powerful single-unit diesel locomotives in the world, with a power output of 3,300 hp (2,500 kW). They had an official maximum speed of 100 miles per hour (160 km/h), however this was frequently exceeded, especially in their lat