British Rail Class 31 diesel locomotives, also known as the Brush Type 2 and originally as Class 30, were built by Brush Traction from 1957-62. They were numbered in two series, D5500-D5699 and D5800-D5862. Construction of the first locomotive was completed in the final week of September 1957, and the handing-over took place on 31 October. The first Class 31 entered service in November 1957, after the launch of the Class 20 locomotive and was one of the Pilot Scheme locomotives ordered by British Railways to replace steam traction. The Railway Technical Centre (RTC) in London Road, Derby, England, was the technical headquarters of the British Railways Board, and was built in the early 1960s. British Rail described it as the largest railway research complex in the world, and certain Class 31s served in a capacity as locomotives aiding experiments and research.