The Midland Railway was formed in 1844 from the merger of the Midland Counties Railway, the North Midland Railway and Birmingham and Derby Junction Railway wit its headquarters in Derby. It expanded its operational territory by acquisition (e.g. railways in the Erewash valley, to Sheffield, serving the Leicestershire coalfields and the route from Birmingham to Bristol), and by construction of new railways and extensions to existing lines, including lines to Peterborough and Lincoln, towards Manchester and, most notably the Settle to Carlisle route. It expanded into the South Wales coalfields, and acquired railways not connected to its main routes: the London, Tilbury and Southend Railway and, in Ireland, the Belfast and Northern Counties Railways. Much of this activity was driven by competition with its geographical rivals, the London and North Western Railway to the west and the Great Northern Railway to the east. Where its interests were better served by co-operation, it tried to reach agreements with those same companies to share routes and traffic receipts. The most famous of these is the Euston Square Confederation, an agreement between the Midland Railway, the London and North Western Railway and the Manchester, Sheffield and Lincolnshire Railway. Other such arrangements were the Cheshire Lines Committee and the right to run over the Great Northern Railway into King’s Cross station. The arrangements for through running and sharing of London termini with its competitors proved unsatisfactory. As a consequence the Midland Railway eventually built its own connection to London. The line ran from Bedford on the Midland’s existing Leicester to Hitchin line, to a terminus at St Pancras. It was opened in 1868. The Midland Railway was a partner in several joint railways e.g. the Somerset and Dorset Joint Railway (with the London and South Western Railway), and the Midland and Great Northern Joint Railway (the Great Northern Railway). The Midland Railway came under the control of the Railway Executive during the First World War and ended its independent existence in 1923 under Grouping when it was merged with, amongst other railway companies, its great rival the London and North Western Railway to form the London, Midland and Scottish Railway Company.

The site of Derby Locomotive Works (the Works) was acquired in 1840 and was originally a facility for the repair of the Midland Railway Company’s railway vehicles: locomotives, carriages and wagons. Locomotive building started in 1851. In 1873 the company relocated the carriage and wagon works to a new site at Litchurch Lane, concentrating locomotive operations at the Works. Eventually, the Works occupied an area of 51 acres. After Grouping the Works became one of two major locomotive factories operated by the London, Midland and Scottish Railway (LMS) (the other being Crewe) and it continued to build locomotives following nationalisation. After 1947 the Works was initially part of the British Transport Commission – Workshops Division, subsequently passing to British Railways Board and then to British Rail Engineering Limited (BREL) in 1970. BREL was privatised in 1989 and the Works closed in 1990. The Works produced its first modern traction, an 0-6-0 diesel shunter, in 1934 and in 1947 built the first mainline diesel-electric locomotive, No. 10000. Locomotive building continued until 1979 along with maintenance and repair. In the later period the Works also manufactured bogies for all traction types and overhauled breakdown cranes for all regions. After privatisation the Works concentrated on supplying bogies and components; locomotive activity ceased.

The London, Brighton and South Coast Railway (LBSCR) was formed on 27 July 1846, when the London and Brighton, and London and Croydon Railways were merged together. The LBSCR stretched from London to Portsmouth and Hastings and the length of the track by the end of 1922 totalled 457 miles. This was comprised of 100 miles of single track, 357 miles of double line, 47 miles with three tracks, 35 miles of four tracks and 14 miles (cumulatively) with five tracks. The LBSCR entered Victoria station in 1860, agreeing to pay half of the costs for the construction of the station. The line from Victoria to Brighton was electrified in three stages, which reached Tulse Hill and West Norwood by 1912. Due to the increasing threat from the tram network the LBSCR decided to use an overhead line instead of a third rail for electrification. In 1893 the line was one of the pioneers of electric lighting in carriages, with 300 coaches lit. The company ran a first-class Pullman service named the "Southern Belle" renamed the "Brighton Belle" in 1934. The service made two trips daily from Victoria to Brighton taking exactly one hour in 1909. LBSCR head offices were in Brighton and the construction of the locomotives took place at Brighton works, locomotives were also built by external contractors, for example Messrs Bury, Curtis and Kennedy, Liverpool. Lancing carriage and wagon works, near Shoreham-by-Sea was built in 1911 in order to relieve pressure of the overcrowded works at Brighton. The first chairman of the LBSCR was Mr C. P. Grenfell, who was succeeded by Samuel Laing in 1848 (previously the Law Clerk in the Railway Department of the Board of Trade). The first secretary was J. Buckton, succeeded by F. Slight in October 1849. R. Jacomb-Hood was the first resident engineer and Peter Clarke was the first manager, however on the 14 February 1848 strong complaints made against Clarke and he was deemed as inefficient and resigned. He was succeeded by George Hawkins. William Stroudly was appointed locomotive superintendent in 1870. In 1899, William Forbes, (son of the General Manager of the Midland Great Western Railway), became General Manager of the London, Brighton and South Coast Railway, where he instigated the programme of overhead electrification. He is also credited with rebuilding Victoria station, extending the Pullman services, and building the Quarry line. During the war he was a member of the Railway Executive. He received a knighthood in 1915. The LBSCR also owned the Terminus Hotel in Brighton and the London and Paris Hotel at Newhaven, to encourage more tourists to use the railway. In 1923, the London, Brighton and South Coast Railway (LBSCR) was absorbed into the Southern Railway, as part of the ‘grouping’ process which organised railway companies into the ‘Big Four’.

The Transport Act 1947 nationalised virtually all British transport, including the railways, waterways, and road haulage. These were transferred to a newly-created operating body, the British Transport Commission (BTC). The British Transport Commission began operations on 1st January 1948, under Chairman Sir (later Lord) Cyril Hurcomb. At this time, the British Transport Commission acquired the “Big Four” grouped railways, with virtually all minor railways as well, together with the London Passenger Transport Board. This automatically transferred the assets of the rail companies to BTC, including ships, ports, hotels, and investments in bus, coach, and haulage companies. Two bus companies, Tilling and Scottish Motor Traction, were soon added, as well as long-distance road hauliers. The Transport Act charged the British Transport Commission with the task of charged with “integrating” various forms of transport into single public service. The British Transport Commission did not directly operate transport services. Operations were delegated to five separately appointed executives: Docks and Inland Waterways, Hotels, London Transport, Road Transport, and Railways. The Railways Executive operated under the name British Railways. In 1949, the Road Transport Executive was divided into two separate executives: Road Haulage and Road Passenger. The Commission exercised financial control over these Executives, and managed them through schemes of delegation. The Commission attempted to fulfil its statutory duty to “integrate” public transport by introducing Area Schemes. These were designed to establish regional monopolies for road passenger transport, ports, and harbours. “Integration” was also to be promoted through Charges Schemes, in which the true costs of different modes of transport were to be reflected in the charges. This was designed to attract traffic to the most economic and efficient mode of transport. The structure of Executives was dramatically altered by the Transport Act 1953, which abolished all Executives, with the exception of London Transport. Responsibility for the operation and maintenance of transport systems was delegated to the chief regional managers. The railways were reorganised into a system of area boards for each of its six regions. In September 1953, Sir Brian Robertson became Chairman. Disposal of the haulage fleet also began at this time, but a lack of buyers made this difficult. Rising costs, industrial action and competition from road traffic meant that the British Transport Commission was in financial trouble by 1955. It sought relief from this by publishing The Modernisation and Re-equipment of British Railways, a plan which proposed an investment in the railways of £1,240m over fifteen years. The main features of this plan were the replacement of steam with electric and diesel traction, the electrification of principle routes, and the introduction of new coaching stock. Despite the modernisation plan, the financial position of the British Transport Commission worsened. Two government reviews, in 1956 and 1959, concluded that the Commission was unwieldy and had an insufficiently commercial outlook. Sir Brian Robertson retired in May 1961, and was replaced by Dr Richard Beeching. The BTC was abolished by the Transport Act 1962. It was replaced with five new authorities that were answerable to the Minister of Transport: the British Railways Board, the British Transport Docks Board, the British Waterways Board, the London Transport Board, and the Transport Holding Company. Dr Beeching became chair of the British Railways Board.