With a reduction in steam traction and the implementation of the Beeching cuts, in March 1964 the decision was taken to move the remaining steam locomotive allocation to the 1950s designed Southall MPD, and reconstruct Old Oak Common as a diesel depot. Within a year the majority of the GWR 1906 depot was demolished, with only "The Factory" repair shop, furthest western turntable and parts of the stores remaining. The main service building had 3 tracks, each holding two locos, with inspection pits, fuel supply points and a washing plant on the approach road. Some of the inspection pits in The Factory were also lengthened and deepened and jacks provided to allow for bogie and spring changing. It opened on 20 October 1965. It was the last of six big diesel depots built for the Western Region, the others being Margam TMD 1960, Bristol Bath Road depot 1960, Laira Traction Maintenance Depot, Plymouth, 1962, Landore TMD, Swansea, 1963 and Cardiff Canton TMD 1964.