High Quality Content by WIKIPEDIA articles! 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, DP1 Deltic, which in turn was named for its Napier Deltic power units. Twenty-two locomotives were built: they dominated express passenger services on the East Coast Main Line (ECML) particularly London – Leeds and London – Edinburgh services until 1978 when InterCity 125 `High Speed Trains` were introduced. 1978–81 saw them gradually relegated to semi-fast or newspaper–parcel–sleeper services along the ECML (destinations including Cleethorpes, Harrogate, Hull, Scarborough and Aberdeen) plus occasional forays `offline` – York - Liverpool Lime Street semi-fast and Edinburgh - Carlisle via Newcastle stoppers. Withdrawal came at the end of 1981. Six locomotives were preserved and are still running today.