Railway – red A geographical map presented restrictions since for sufficient clarity of detail in the crowded central area of the map required the extremities of the District and Metropolitan lines to be omitted and so a full network diagram was not provided. The problem of truncation remained for nearly half a century. Although all of the western branches of the District and Piccadilly lines were included for the first time in 1933 with Harry Beck's first proper Tube map, the portion of the Metropolitan line beyond did not appear until 1938, and the eastern end of the District line did not appear until the mid-1950s. The route map continued to be developed and was issued in various formats and artistic styles until 1920, when, for the first time, the geographic background detail was omitted in a map designed by MacDonald Gill. That freed the design to enable greater flexibility in the positioning of lines and stations. The routes became more stylised but the arrangement remained, largely, geographic in nature. The 1932 edition was the last geographic map to be published before Beck's diagrammatic map was introduced. Beck's maps The first diagrammatic map of London's rapid transit network was designed by Harry Beck in 1931. He was a London Underground employee who realised that because the railway ran mostly underground, the physical locations of the stations were largely irrelevant to the traveller wanting to know how to get from one station to another; only the topology of the route mattered. That approach is similar to that of electrical circuit diagrams although they were not the inspiration for Beck's map. His colleagues pointed out the similarities, however, and he once produced a joke map with the stations replaced by electrical circuit symbols and names, with terminology such as "Bakerlite" for the Bakerloo line. To that end, Beck devised a simplified map with stations, straight-line segments connecting them, and the River Thames; and lines running only vertically, horizontally, or on 45° diagonals. To make the map clearer and to emphasise connections, Beck differentiated between ordinary stations, marked with tick marks, and interchange stations, marked with diamonds. London Underground was initially sceptical of his proposal since it was an uncommissioned spare-time project and was tentatively introduced to the public in a small pamphlet in 1933. However, it immediately became popular, and the Underground has used topological maps to illustrate the network ever since.