DP2, meaning Diesel Prototype number 2, was a prototype Type 4 mainline diesel locomotive built in 1962 by English Electric at their Vulcan Foundry in Newton-le-Willows to demonstrate its wares to British Railways. As the Deltics were then in production, it was decided to produce the locomotive on the same production line; the bodyshell used for DP2 reputedly being the eighteenth made. While DP2 looked like a Class 55 locomotive in outline, there were many detail differences; particularly the large bodyside radiator vents at one end, and the single roof fan as opposed to the four symmetrically placed fans on the Deltics. These differences were the external effect of DP2 being totally different from the twin-engined Deltics internally, being the forerunner of the Class 50.