The English Electric prototype DP1 entered service with British Rail (BR) in October 1955. Although officially numbered DP1 (Diesel Prototype 1), this was never carried on the locomotive, it being emblazoned instead with the word DELTIC in large cream letters on its powder-blue sides. Plans to name the locomotive Enterprise
never came to fruition and it was forever known to everyone simply as ‘Deltic’.
The locomotive first saw service on the London Euston-Liverpool Lime Street route on the London Midland Region of British Railways (BR). However, the intention soon became apparent for the need to electrify the major routes on that region. In January 1959 DP1 was moved to the Eastern Region, which wanted to test the locomotive on its East Coast Mainline (ECML) express services between London King's Cross and Doncaster.
A severe phasing gear oil leak saw the locomotive declared a failure In November 1960 which ultimately resulted in DP1 being withdrawn officially in March 1961, by which time the production Class 55 locomotives were coming into service. It was returned to the English Electric Vulcan Foundry having completed 450,000 successful miles in service. A project to repair the locomotive and move it to Canada for trials and hopes of an export order came to nothing and instead following storage it was donated to the Science Museum in London as part of its transport exhibition.
A review of the museums collection in the 1980s led to a new home being sought and it was the National Railway Museum
(NRM) in York that provided accommodation for the locomotive, arriving there in October 1993. The locomotive now resides in the sister site of the NRM in Shildon, County Durham.