When British Railways was created at the start of 1948, it was immediately subdivided into six Regions, largely based upon pre-nationalisation ownership.

[1] To this was added some minor railways and joint lines in which the GWR had an interest:[2] Regional boundaries were adjusted several times in subsequent years.

Adjusted for transfer of Banbury northward to LMR and Dorset, Devon and Cornwall from SR, the assets of WR reduced greatly over the decade 1955–1965 and especially from 1963 to 1965:[5] Major new investment in infrastructure did not go ahead substantially until after 1955.

The earliest projects included the rebuilding of stations at Banbury and Plymouth, both postponed since the 1940s; of less long-term relevance were new facilities at Paignton for summer holiday passenger traffic and a marshalling yard at Margam in South Wales.

The Western Region built a large number of steam locomotives to GWR designs including 341 pannier tanks, even after the advent of diesel shunters.