British Rail Class 55

The British Rail Class 55, nicknamed Deltic after its twin Napier Deltic engines, is a class of diesel locomotive built in 1961 and 1962 by English Electric at the Vulcan Foundry for British Railways, with 22 units produced. A Co-Co diesel-electric weighing 99 long tons, it produced 3,300 horsepower, making it the most powerful single-unit diesel locomotive in the world when introduced, with an official top speed of 100 miles per hour though capable of exceeding 125 in service. Built for high-speed express passenger service on the East Coast Main Line between Edinburgh and London King's Cross, the Deltics introduced the first regular 100 mile-per-hour diesel passenger service in Britain and, once fully deployed in 1962, cut the London-Edinburgh journey time from seven hours to six. They operated for about 20 years before being displaced by InterCity 125 trains from 1978, and six of the 22 survive in preservation.