A poster of Beck's iconic map of the London Underground System.

The plan shows both the central line under construction from Liverpool Street to Ongar, and from North Acton to Denham; and the Northern Line from Finsbury Park to Alexandra Palace, High Barnet, and Bushey Heath. The extensions to the network were part of the 'New Works Programme' (from 1935 to 1940), a major investment programme by London Transport. The plan can be dated by the text below Highgate "(from Summer of 1940 only)". By June of 1939 the Northern line extension from Archway to East Finchley had been completed, although excluding Highgate station as shown on the plan. The extension to High Barnet, shown here as under construction, would not be open until 14th April 1940.

The map was designed by the 29 year-old engineer Harry Beck. Abandoning the restrictions of a geographically correct layout, the map actually constitutes a diagram of the network, showing relationships rather than distances to scale. By using only verticals, horizontals and diagonals, and adopting a clear colour scheme, Beck created a design classic, both easy to use and aesthetically appealing. After the positive public response to the limited trial run issued in 1932, the design was formally adopted in 1933, becoming an essential part of London Transport's campaign to project itself as a modern, rational and efficient system. The design remains in use to this day, having become essential to the comprehensibility of complex transport networks all over the world.