 This was a major exercise, requiring the rebuilding of most of the stations, and cutting a second bore for the Slade tunnel.The Southern Railway era started with the Railways Act 1921 and the grouping of the railways.This took effect on 1 January 1923, when the LSWR was absorbed into the new Southern Railway along with its southerly neighbour, the London, Brighton and South Coast Railway and the South Eastern and Chatham Railway.