The type was developed for the Western Region of British Railways, which had opted for lightweight locomotives with hydraulic transmission when allocated funds under the British Railways Modernisation Plan of 1955. One hundred and one of the class were built between 1961 and 1964 when it became apparent that there was a requirement for a medium power diesel-hydraulic design for both secondary passenger work and freight duties.
They were allocated to Bristol Bath Road, Cardiff Canton and Old Oak Common. None of the class was named. Withdrawal from service began in 1971, and by 1975 all had been withdrawn. Their early withdrawal was caused, primarily, by BR classifying the hydraulic transmission as non-standard. Four examples survived into preservation.