The British Rail Class 55 is a class of diesel locomotive built in 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, British Railways DP1 DELTIC (the running number DP1 was never carried), which in turn was named after its Napier Deltic power units.