The competition severely strained the resources of both companies, the LCDR given its later start, and the SER with neighbouring LBSCR to the west in Sussex and Surrey. Co-operation broke out with a joint line between Dover and Deal, but despite a carve up agreement of coastal traffic, competition still persisted leading to Thames terminals being constructed in the middle of the North Kent marshes by both companies (the Hundred of Hoo Railway and the Port Victoria branch). Eventually a "merger" by form of a "managing committee" (to avoid capital gains tax) was agreed and the South Eastern and Chatham Railway (SECR) was formed in 1899. Only some minor rationalisation was able to occur prior to World War I (the SER's Chatham branch closed, various connecting chords were constructed, etc.). In the aftermath of World War I, with the SECR having borne extensive amounts of war traffic, the government "grouped" all the railway companies together, with the SECR joining neighbouring LBSCR and LSWR in the Southern Railway in 1921. Southern kept closed some inner London routes closed under wartime austerity measures, but embarked upon continuing SECR's rationalisation and a roll out of 660 V DC third rail electrification that had been successfully initiated by LSWR pre war. During the 1920s the inner suburban lines were electrified out to Dartford, Bromley and Orpington (1924–26). The 1930s saw the outer suburban services electrified; Sevenoaks (1935) and Gillingham (1939) and Maidstone West (1939). Electric traction thus epitomised the growth of commuting and the spread of the London commuter belt. The major item of rationalisation was the extensive work on Thanet, which saw the duplication removed. World War II further devastated the railways, and post war the government nationalised the railways, forming British Railways in 1948, with Southern being placed in the Southern Region. The 1955 British Transport Commissioners report planned out a major investment programme in the railways and Kent Coast Electrification was one of the 5 key projects. This saw the main lines to the ports electrified in two stages between 1959 and 1961. The signally was upgraded, new rolling stock purchased, platforms significantly lengthen and the track was widened between Bickley Junction and Swanley. However, despite this massive investment, several remote lines were closed due to declining traffic and the infamous Beeching report. From the 1950s through to the 1980s branches closed including: Hawkhurst, Elham Valley, Canterbury and Whitstable Railway, Hythe,