End of the line: 1939 onwards
Underground trains took over from LNER steam services between East Finchley and High Barnet on 14 April 1940. LNER Services were withdrawn between Highgate and East Finchley in March 1941 (both services having briefly operated to the latter station from the two parts of station. Underground trains began serving in May 1941, but never ran to Edgware as planned.
In 1942, the Finsbury Park-Highgate-Alexandra Palace line was reduced to a peak service shuttle to Finsbury Park, ending through running to central London.
After the war, the introduction of London's Metropolitan Green Belt made the project to continue the line to Bushey unnecessary, as the intended housing development proposed in the area was prevented by the new legislation. The plan was formally cancelled in October 1950. In 1953, the modernisation and electrification of the remaining sections of track between Mill Hill East to Edgware, and Finsbury Park to Alexandra Park, were also abandoned.
The last regular passenger service between Finsbury Park, Highgate and Alexandra Palace ran on 3 July 1954. In 1957, the goods yards at Cranley Gardens and Muswell Hill were closed, and the line from Park Junction (Highgate Station) to Alexandra Palace was abandoned.
The line from Finsbury Park to Edgware continued to be used for goods traffic, primarily coal, milk and building materials, even into the period when diesel engines had replaced steam locomotion. However, the introduction of the Clean Air Act 1956 established a shift away from coal as a fuel for domestic heating and the demand for coal slumped. At the same time, the expansion of road haulage reduced the demand for rail transportation of other bulk loads and the line closed completely between Edgware and Mill Hill East in 1964, with equipment and track removed by the following year.
London Underground regularly moved stock for the Northern City Line along the old lines between Highgate Wood depot, Finsbury Park and Drayton Park depot until September 1970. The movements ran regularly on Tuesdays, and occasionally on Mondays and Wednesdays. The tracks were removed in 1971, following which the Northern City Line empty stock movements ran from Neasden, via King's Cross (York Road), and the Widened Lines.[8] The sections of the line from Finsbury Park to the southern portals of the southern tunnels at Highgate station, and between the sites of Cranley Gardens and Muswell Hill stations, now form a rail trail known as Parkland Walk. Stretches of the Mill Hill East to Edgware line are now local nature reserves: Copthall Railway Walk and Mill Hill Old Railway Nature Reserve.
