The British Rail Class 04 0-6-0 diesel-mechanical shunting locomotive class was built between 1952 and 1962 . It was the basis for the later Class 03 built in the British Railways workshops . The British Rail Class 04 0-6-0 diesel-mechanical shunting locomotive class was built between 1952 and 1962 and was the basis for the later Class 03 built in the British Railways workshops .