After the 1921 Railways Act created the Big Four railway companies, the line was, from 1923, part of the London & North Eastern Railway (LNER). The section of the High Barnet branch north of East Finchley was incorporated into the London Underground network through the "Northern Heights" project begun in the late 1930s.
For the introduction of London Underground services, the Victorian station was completely demolished and was rebuilt to an Art Deco/Streamline Moderne design by Charles Holden. As part of the rebuild, the station was provided with two additional platforms, giving four in total . This was necessary as the original intention of the "Northern Heights" project was that trains would be able to run south from East Finchley via two routes. One route would have run over the existing tracks to LNER's Highgate station (above ground and now derelict) and onwards via Crouch End to Finsbury Park: this route was never completed. The other route ran through newly constructed tunnels running into a new deep-level Highgate station built under the LNER one and onwards to Archway, Camden Town and central London: this is the route south of East Finchley as it now exists.
The platforms comprise two parallel islands with tracks on both sides. The inner pair of tracks served the 'high level' route to Highgate, whilst the outer pair served the tunnel route. Underground trains first served the station on 3 July 1939 which acted as a temporary terminus for the Northern Line whilst the electrification of the line to the north was completed. Northern Line services to High Barnet began on 14 April 1940. The station continued to be served by LNER steam trains from Highgate (High-level) station until 2 March 1941 when that service was discontinued. The inner platforms are now generally used only by trains starting or terminating at East Finchley and those coming from or going to the depot south of the station.
After the war, most of the remaining plans of the "Northern Heights" project were cancelled and the section of the LNER line from East Finchley to Finsbury Park was not incorporated into the Northern Line. Underground services never ran from East Finchley through Highgate 'high level' station as planned although the line was occasionally used for Underground stock transfers up to its complete abandonment in 1970.
Like the other stations that Holden designed for London Underground in the 1930s, East Finchley station was at the forefront of Britisharchitectural design and took inspiration from European architecture (particularly Dutch) that Holden had seen on trips to the continent during that decade. The track here runs roughly north-west to south-east. The imposing station building, built on rising ground adjacent to the railway bridge over High Road (A1000), has two entrances. The main entrance is at the south-east end of the station. It is on the north-east side of the tracks facing High Road. There is also a smaller, secondary entrance at the north-west end, on the south-west side of the tracks, at the end of an access road called "The Causeway". It is possible to walk through the station from one exit to the other without going onto the platforms.
A strong feature of the station is the semi-circular glazed stairways leading to the enclosed bridge over the tracks occupied by staff offices. These, combined with the station's block-like mass and the narrow deck-like platform buildings, lend the building the atmosphere of a ship. Prominent from the platforms and dominating the main entrance elevation, almost like a ship's figurehead, is a Category:Aldwych Branch
The Short Streach Of Line Between Holborn And Aldwych Was Closed In 1994.The Line Was Due To be extended to Waterloo but never was.There will be a bit of Aldwych In My Website when added statue by Eric Aumonier of a kneeling archer captured as if having just released an arrow along the railway line towards central London. (The Archer, a local community newspaper, is named after this landmark). The archer is intended to commemorate Finchley's ancient association with hunting in the nearby Royal Forest of Enfield. There is also a pun, in that it faces towards Archway.
Americanchat show host and former mayor of Cincinnati, Ohio, Jerry Springer claims he was born inside the station on 13 February 1944, during the Blitz, but he may be mistaken and it's more likely that it was Highgate station where his mother was sheltering since there is no deep shelter at East Finchley, a surface station.
It is often used for film and television productions, because of its outward appearance, for example in Home and Away.