improvement scheme for the A5 road (now renumbered the A5183 at this point). Construction works on the Northern Heights project began in the late 1930s but were interrupted by the outbreak of the Second World War. Most of the work undertaken to that date had been carried out on the existing LNER branch tracks but work between Edgware and Bushey Heath had started in June 1939. The route of the line had been cleared and laid out and some earthworks and tunnelling carried out between Edgware and Elstree South. Following the outbreak of war in Europe, work on the extension was suspended in September 1939 and was formally terminated in December of the same year as wartime funding restrictions would prevent completion. During the war years, the LPTB-owned land was used for farming vegetables for staff canteens. Cancellation The sites of all three new stations were in semi-rural locations and, as it had elsewhere, it was intended that the opening of the new section of Underground line would stimulate the construction of new residential estates that the stations would then serve. After the war, new legislation was introduced to limit the continuing expansion of urban areas into their surrounding countryside. This legislation created the Metropolitan Green Belt around London and the area designated included the area covered by the new Northern line extension. Without the possibility of constructing the new housing estates, the new line had no purpose and the plans for the extension were cancelled in 1950. The tunnelling shields were removed in 1949 and the tunnels sealed. The entrances were finally buried in the 1960s when the M1 motorway was constructed and today nothing is visible on the surface. See also Edgware, Highgate and London Railway - LNER branch line taken over by London Underground as part of the Northern Heights project Notes and references Notes References Bibliography External links Abandoned Tube Stations - Northern Heights: Edgware - Bushey Heath Hertsmere Rail transport in Hertfordshire Proposed London Underground stations Unbuilt Northern Heights extension stations Charles Holden railway stations