During the First World War the government had taken control of the railways to co-ordinate the war effort. After the war ended it was decided that the railway companies could not competitively return to their prior state, and so the 120 existing railway companies were combined into four companies, which became known as the ‘Big Four’’. The London Midland and Scottish Railway, also known as the LMS, was founded on 1 January 1923. The London and North Western Railway (LNWR), Midland Railway (MR), Lancashire and Yorkshire Railway (LYR), North Staffordshire Railway (NSR), Highland Railway (HR), Furness Railway (FR), Glasgow and South Western Railway (G&SWR) and Caledonian Railway (CR) were merged. These eight large constituent companies were joined by 27 other smaller subsidiary railways. The LMS covered the Western half of the country, stretching from the London and the Midlands, through Yorkshire, Lancashire, and up to Scotland. In all the LMS had a total of 7,790 miles of track, which made it the largest railway of the Big Four. The London termini of the LMS were St. Pancras and Euston stations and it had works at Crewe, Horwich, Wolverton and Derby amongst other locations. In 1934 the LMS moved into a new headquarters at Euston House on Seymour Street (later renamed Eversholt Street) in London. Charles Napier Lawrence, 1st Baron Lawrence of Kingsgate was the first appointed chairman of LMS, he had previously been the chairman of the LNWR between 1921-1923. He was chairman of the LMS for one year, and was succeeded by Sir Guy Granet. The management structure was headed by a chairman and a deputy chairman, there was a board of directors that had initially had 20 members, made of men who previously worked for the constituent companies. The first General Manager was Arthur Watson from the LYR. There was a Deputy General Manager for Scotland, a post first held by D.A. Matthieson, formerly of the CR. J.H. Follows, from the Midland Railway, was the first Chief General Superintendent and S.H. Hunt, formerly of the LNWR, was the first Chief Goods Manager. The post of Chief Engineer was initially held by E.F.C. Trench, formerly employed by the LNWR. The first Chief Mechanical Engineer was G. Hughes from the LYR and his deputy was Sir Henry Fowler, from the Midland Railway. The management structure was re-organised from January 1926 and an Executive was set up, Sir Josiah Stamp was the first President of the Executive. From January 1927 four Vice-Presidents were appointed to replace the general managers on the Executive committee. The line was divided up for operational management into three geographical divisions, which were called Western, Midland and Northern. Each division was overseen by a General Superintendent who reported to the Chief General Superintendent. The main line of the LMS ran from London Euston to Wick over 729 miles. The LMS ran a number of joint railways with the London & North Eastern Railway and the Southern Railway. It ran the Cheshire Lines Committee, the Midland and Great Northern line between Peterborough, the Norwich and Lowestoft and the Manchester, South Junction and Altrincham suburban line with the London & North Eastern Railway. It also joined forces with the Southern Railway to run the Somerset and Dorset line between Bath, Burnham and Bournemouth. The LMS undertook a limited programme of electrification, mainly focusing on suburban lines in London and Manchester. The LMS owned many hotels, including the Queen’s Hotel in Leeds and the iconic Art Deco Midland Hotel at Morecombe Bay. The LMS also ran passenger steamers from Holyhead, Heysham and Stranraer over the Irish Sea to Northern Ireland and the Republic of Ireland. Following the 1947 Transport Act which nationalised the railways, the concerns of the LMS were taken over by the Railway Executive as part of the British Transport Committee. Within the Railway Executive, British Rail: London Midland Region assumed responsibility for the LMS’s former area of operations.

During the First World War the government took control of the railways to co-ordinate the war effort. After the war it was decided that the railway companies could not competitively return to their prior state, and so the 1921 Railways Act merged the 120 existing railway companies into four companies, which became known as the ‘Big Four’’. Founded in 1923, the Southern Railway took over the railways of South-East England and came to consist of five major railway companies and 14 small ones. The Southern Railway had works at Ashford, Brighton, Lancing and Eastleigh. The first chairman of the Southern Railway was Brigadier-General Sir Hugh Drummond. Initially the general managers of the three main constituent companies, namely the London & South Western Railway (LSWR), London, Brighton & South Coast Railway (LBSCR) and South Eastern and Chatham Railway (SECR) worked together to lead the Southern Railway during its first year of operation. From 1 January 1924 it was decided that railway would be led by one general manager and one chief mechanical engineer. The first holders of these posts were Sir Herbert Ashcombe Walker, formerly manager of the LSWR and Richard Maunsell previously the Chief Mechanical Engineer of the SECR. Walker was succeeded by Gilbert Szlumper, then Sir Eustace Missenden and the last general manager prior to nationalisation was Sir John Elliott. The Southern Railway's operating structure was based on geographical divisions, initially these were London (East), London (West), Eastern (Dover) Southern (Brighton), Central (Southampton), and Western (Exeter). The Southern Railway was the smallest of the Big Four, and it relied primarily on passenger traffic. The Southern Railway’s predecessors had begun the process of electrification around suburban London where there was a high volume of passenger traffic. This programme was continued by the Southern Railway and was approved by its first AGM in March 1924. A rolling programme of electrification continued throughout Southern Railway’s operation, and on 30 December 1932 the newly electrified line to Brighton was opened. Despite Southern Railway’s increasing use of electric trains, steam locomotives continued to be used, especially for goods trains, until the nationalisation of the railways in 1948. As well as operating rail traffic, the Southern Railway owned and operated docks and harbours along the South Coast, the most important of which was Southampton Docks. It also ran passenger steamers across the English Channel to France. The Southern Railway operated air services to the Channel Islands from a number of airfields in the South-East and had stations at these airfields to allow passengers to transfer. The 1947 Transport Act nationalised the railways, and the Southern Railway came to be run by the Railway Executive as part of the new British Transport Commission. The Southern Railway’s rail operations were taken over by the Southern Region of British Railways.