Tower Bridge as its northern landfall is in Tower Hamlets. The bridge consists of two bridge towers tied together at the upper level by two horizontal walkways, designed to withstand the horizontal tension forces exerted by the suspended sections of the bridge on the landward sides of the towers. The vertical components of the forces in the suspended sections and the vertical reactions of the two walkways are carried by the two robust towers. The bascule pivots and operating machinery are housed in the base of each tower. Before its restoration in the 2010s, the bridge's colour scheme dated from 1977, when
London Bridge station to the Big Four grouping in 1923. All of the railways of southern England combined to form the Southern Railway (SR), bringing the London Bridge complex under single ownership. The wall that divided the Chatham and Brighton stations was partially knocked through in 1928 to provide an easier interchange between stations. This allowed a greater range of platforms to be used for the increasingly frequent suburban rail services to London Bridge. Between 1926 and 1928 the Southern Railway electrified the SE&CR suburban lines at London Bridge using a third rail system, adapting the existing LB&SCR routes to it at the