The Southern Railway was the smallest of the 'Big Four' railway companies created under the Railways Act 1921 having a route mileage of 2,129 miles stretching London in the north to Plymouth in the south and from Ramsgate in the east to Padstow in the west. Its ships served France and the Channel Islands. Its principal revenue came from passengers and not goods traffic unlike the other three companies. In many ways it was the most progressive of the four being the only one to go for extensive electrification. This volume covers the years 1923 from the Company's formation to 1935 and the completion of the first stage of the main line electrifications.As well the electrification of the Southern's entire suburban system and the beginning of the main line electrifications the years saw a number of other major works including the re-signalling of Waterloo Station and the rebuilding of stations in Hastings, Dover and Southampton along with improvements to Southampton Docks.The Railway had to fight growing competition from bus and coach operators for domestic services and airlines for international services. The Company invested in both bus companies and in Imperial Airways and later participated in Railway Air Services.

Its motive power was varied with at the formation of the company some locomotives dating back to mid 1860s and some only recently built. To these were added a variety of classes including the less than successful Lord Nelson Class and the very successful Schools Class.