The London, Chatham and Dover Railway was a railway company in south-eastern England created on 1 August 1859, when the East Kent Railway was given parliamentary approval to change its name. Its lines ran through London and northern and eastern Kent to form a significant part of the Greater London commuter network. The company existed until 31 December 1922 when its assets were merged with those of other companies to form the Southern Railway as a result of the grouping determined by the Railways Act 1921. The railway was always in a difficult financial situation and went bankrupt in 1867, but was able to continue to operate. Many of the difficulties were caused by the severe competition and duplication of services with the South Eastern Railway (SER). However, in 1898 the LCDR agreed with the SER to share the operation of the two railways, work them as a single system and pool receipts: but it was not a full amalgamation. The SER and LCDR remained separate companies with separate shareholders until both becoming constituents of the Southern Railway on 1 January 1923.

The Southern Railway (SR), sometimes shortened to 'Southern', was a British railway company established in the 1923 Grouping. It linked London with the Channel ports, South West England, South coast resorts and Kent. The railway was formed by the amalgamation of several smaller railway companies, the largest of which were the London and South Western Railway (LSWR), the London, Brighton and South Coast Railway (LB&SCR) and the South Eastern and Chatham Railway (SE&CR). The construction of what was to become the Southern Railway began in 1838 with the opening of the London and Southampton Railway, which was renamed the London & South Western Railway.