Class D3/6 were diesel shunters built in 1935 by English Electric for the London, Midland and Scottish Railway. They were the first of a new design of diesel shunters based on the English Electric 6K of 350 horsepower (260 kW) diesel engine. Similar prototypes were built for the Southern Railway (SR1-3), Great Western Railway (GWR2), and London and North Eastern Railway (8000-8004). They were all substantially similar, with the long bonnet ("nose"), 0-6-0 wheel arrangement, EE 6K prime mover and 2 axle-hung traction motors. This configuration was repeated in most subsequent large diesel shunters built in Britain, such as the British Rail Class 11 and even more numerous British Rail Class 08 that entered service after World War II.