Archway to East Finchley and to the Northern City line with a new surface connection between Drayton Park and Finsbury Park. The line from Finchley Central to Edgware closed for electrification and reconstruction on 11 September 1939. The station was first served by electric Northern line trains on 14 April 1940 when the service was extended from East Finchley to High Barnet. After a period where the station was serviced by both operators, LNER steam services were ended on 2 March 1941. Following the outbreak of the Second World War in September 1939, completion of the electrification works on the line to Edgware was slowed and was completed only as far as Mill Hill East. Northern line services to Mill Hill East began on 18 May 1941 to serve the nearby Inglis Barracks. Postwar After the war, the plans to complete the Northern Heights works were reviewed but were not restarted. Maintenance works and reconstruction of war damage on the existing network had the greatest demand for LPTB funds. Funds for new works were severely limited and priority was given to the completion of the western and eastern extensions of the Central line to West Ruislip, Epping and Hainault. A government-commissioned review of rail transport in the London area produced a report in 1946 that proposed many new lines. It anticipated that completion of the Northern Heights works would put pressure on the Northern line's capacity and it proposed that a relief line should be considered for one or other of the two branches. One of these, designated Route 12B, was proposed to run as a tube line in tunnel from Finchley Central to Clapham Junction via Golders Green, St John's Wood, Baker Street, Knightsbridge and Sloane Square. Despite being shown as under construction on underground maps as late as 1950, work never restarted on the unimplemented parts of the Northern Heights plan. The proposal for Route 12B was also not developed by the LPTB or its successor organisations. Before the war, Charles Holden and Reginald Uren designed replacement station buildings to be built on both sides of the road bridge at the north end of the station. The curtailment of the Northern Heights Plan means that the rebuilding work was not implemented and the station still retains much of its original Victorian architectural character today. As one of two EH&LR stations retaining its original buildings (the other is Mill