sentences:  In 1923, the Westerham Valley branch, together with its operators the SECR, became part of the Southern Railway at the grouping.The Southern Railway was nationalised in 1948 and became the Southern Region of British Railways.The line began to suffer competition with buses, notably the 403 route which ran from Croydon via Sanderstead, Chelsham and Westerham to Sevenoaks, and as train fares rose dramatically from 1938, passenger numbers fell.