Northern line

Formation The core of the Northern line evolved from two railway companies: the City & South London Railway (C&SLR) and the Charing Cross, Euston & Hampstead Railway (CCE&HR). The C&SLR was London's first electric hauled deep-level tube railway. It was built under the supervision of James Henry Greathead, who had been responsible for the Tower Subway. It was the first of the Underground's lines to be constructed by boring deep below the surface and the first to be operated by electric traction. The railway opened in November 1890 from Stockwell to a now-disused station at King William Street. This was inconveniently placed and unable to cope with the company's traffic so in 1900 a new route to Moorgate via Bank was opened. By 1907, the C&SLR had been further extended at both ends to run from Clapham Common to Euston. The CCE&HR, commonly known as the "Hampstead Tube", was opened in 1907 and ran from Strand (nowadays Charing Cross) via Euston to Camden Town with branches splitting to Golders Green and Highgate (nowadays Archway). It was extended south by one stop to Charing Cross (nowadays Embankment) in 1914 to form an interchange with the Bakerloo and District lines. In 1913, the Underground Electric Railways Company of London (UERL), owner of the CCE&HR, took over the C&SLR although they remained separate companies for some time. Integration During the early 1920s a series of works were carried out to connect the C&SLR and CCE&HR tunnels to enable an integrated service to be operated. The first of these new tunnels between the C&SLR's Euston and CCE&HR's Camden Town stations had originally been planned in 1912 but was delayed by the First World War. Construction began in 1922 and this first tunnel opened in 1924. The second connection linking the CCE&HR's Embankment and C&SLR's Kennington stations opened in 1926. It provided a new intermediate station at Waterloo to connect to the main line station. The smaller diameter tunnels of the C&SLR were also enlarged to match the standard diameter of the CCE&HR and other deep tube lines. In conjunction with the works to integrate the two lines, two major extensions were undertaken: northwards to Edgware in Middlesex and southwards to Morden in Surrey. The Edgware extension used plans dating back to 1901 for the Edgware and Hampstead Railway which the UERL's subsidiary, the London Electric Railway, had taken over in 1912. It extended the CCE&HR line from its terminus at Golders Green to Hendon Central in 1923 and to Edgware in 1924. The line crossed open countryside and ran mostly on viaduct from Golders Green to Brent and then on the surface, apart from a short tunnel north of Hendon Central. Five new stations were built to pavilion-style designs by Stanley Heaps, stimulating the rapid northward expansion of suburban developments in the following years. The engineering of the Morden extension of the C&SLR from Clapham Common to Morden was more demanding, running in tunnel to Morden station which was then constructed in a cutting and the line continued a bit beyond to the depot. The extension was initially planned to continue to Sutton over part of the route of the unbuilt Wimbledon and Sutton Railway (in which the UERL held a stake) but agreements were made with Southern Railway (SR) to end the extension at Morden, the SR building a surface line from Wimbledon to Sutton in the 1930s via South Merton and St. Helier. The tube extension itself opened in 1926 with seven new stations all designed by Charles Holden in a modern style. Owing to the complicated nature of the resulting line, it became known as the Morden–Edgware line, although a number of alternative portmanteau names were mooted in the fashion of the Baker Street and Waterloo Railway becoming the Bakerloo line, such as "Edgmor", "Mordenware", "Medgeway" and "Edgmorden" lines. After the UERL and the Metropolitan Railway (MR) became unified under the London Passenger Transport Board (LPTB) in 1933, the MR's Great Northern & City Railway subsidiary, which ran mostly underground from Moorgate to Finsbury Park, transferred management to the Morden–Edgware line, branding itself as the Northern City line. Northern Heights plan Following the formation of the LPTB, in June 1935 the organisation proposed the New Works Programme, an ambitious plan to expand the Underground network in response to London's growing suburban population and to relieve congestion on the existing steam-operated suburban lines. In the case of the Morden–Edgware, these were the London and North Eastern Railway (LNER) suburban lines north of Highgate, built in the 1860s and 1870s by the Edgware, Highgate and London Railway (EH&LR) and its successors, running from Finsbury Park to Edgware via Highgate, with branches to Alexandra Palace and High Barnet. The Morden–Edgware line's project, known as the Northern Heights plan owing to the high ground in north London, involved fourth-rail electrification of the surface lines and the double-tracking of the single-line section between Finchley (Church End) and Edgware. The Northern Heights plan also called for the construction of three new linking sections of track: between the Northern City line and new surface level platforms at Finsbury Park; a deep-level tunnel from Archway to East Finchley; and a diversion of the Mill Hill branch to the LPTB's Edgware station. As a result of the project's name, the Morden–Edgware line was renamed as the Northern line on 28 August 1937. Work began on the initial stages of the extensions in 1936, as did that on Bushey Heath following its authorisation in 1937, with completion projected by 1941. The tunnelling northwards from Archway was the first element to be completed and an initial service to the rebuilt East Finchley station commenced on 3 July 1939, though trains skipped the deep-level platforms at Highgate until its fitout was completed by 19 January 1941. Further progress was disrupted by the start of the Second World War in September 1939; however enough development had been made to complete the electrification of the High Barnet branch, over which tube services started on 14 April 1940, and the single-track LNER line to Edgware being electrified as far as Mill Hill East, reopening as a tube service on 18 May 1941 to serve the nearby Inglis Barracks. The partially-complete depot at Aldenham was converted into an aircraft factory, constructing Handley Page Halifax bombers as part of the war effort. Other work on the extension that were eventually halted during the Second World War included the construction of a viaduct at Brockley Hill and a tunnel near Elstree South which started in June 1939, the laying of a second line as far as Mill Hill (The Hale) and the construction of its second platform. Independent of the Northern Heights plan was an intention to introduce nine-car trains on the Northern line as a response to severe overcrowding. While several existing surface station platforms were lengthened to accommodate two additional cars, the deep-level platforms were not easily rebuilt, although Highgate's new platforms were built nine-car trains in mind, so selective door operation was introduced whereby two cars of the train had its doors locked in the tunnel. Nine-car operations began in November 1937 between Edgware and Kennington via Charing Cross, with ten new 1938 Stock trains being fitted with selective door operation. By the start of the War, nine-car trains were discontinued and never revived. After the war, much of the area beyond Edgware was made part of the Metropolitan Green Belt that largely prevented the anticipated residential development, thus the potential demand for services from Bushey Heath vanished. Although efforts were made to complete Aldenham Depot as an Underground facility, from December 1947 it was modified for use as a heavy repair works of bus bodies, supposedly temporarily until Aldenham was required for railway purposes. Following the extension's cancellation, the depot was converted into an overhaul facility for buses, serving this purpose until 1986. The introduction of electric services to High Barnet and Mill Hill East undermined passenger numbers on the remaining LNER-operated lines. Consequently, passenger services to Mill Hill (The Hale) and Edgware, having been suspended in September 1939 to allow works to be completed, never resumed Tickets were still being sold to and from Mill Hill (The Hale) until the late 1960s, with passengers being directed onto the 240 bus to connect with the Underground. Further proposals included building additional tunnels between Kennington and Tooting Broadway to relieve congestion, with alternative duplication suggested between Golders Green and Waterloo. In the 1980s, an extension of the Northern line to Peckham Rye and Streatham Hill was proposed as part of a review of potential extensions of Underground lines. Between 1989 and 1992, Angel tube station was rebuilt with a new northbound tunnel alongside the existing station platforms which were widened to become the new southbound platform, replacing the old narrow platforms which by then had become a safety hazard with increased passenger ridership. A similar project was undertaken at Euston in the 1960s in conjunction with the construction of the Victoria line By the early 1990s, the line had deteriorated due to years of under-investment and the use of old rolling stock, most of which dated back to the early 1960s. The line gained the nickname "Misery Line" due to its perceived unreliability. In 1995, a comprehensive refurbishment of the line began – including track replacement, power upgrades, station modernisation (such as Mornington Crescent) and the replacement of older rolling stock with new 1995 Stock thanks to a public–private partnership deal with Alstom. The Northern line was originally scheduled to switch to automatic train operation in 2012, using the same SelTrac S40 system as used since 2009 on the Jubilee line and for a number of years on the Docklands Light Railway. Originally the work was to follow on from the Jubilee line so as to benefit from the experience of installing it there, but that project was not completed until spring 2011. Work on the Northern line was contracted to be completed before the 2012 Olympics. It was then undertaken in-house, and TfL predicted the upgrade would be complete by the end of 2014. The first section of the line (West Finchley to High Barnet) was transferred to the new signalling system on 26 February 2013 and the line became fully automated on 1 June 2014, with the Chalk Farm to Edgware via Golders Green section being the last part of the line to switch to ATO. Since the mid-autumn of 2016, a 24-hour "Night Tube" service has run on Friday and Saturday nights from Edgware and High Barnet to Morden via the Charing Cross branch; service is suspended on the Bank branch during these times. Trains run every eight minutes between Morden and Camden Town and up to every 16 minutes on the Edgware and High Barnet branches. Labour disputes delayed the planned start date of September 2015. In January 2018, Transport for London announced that it would double the period during which it runs peak evening services in the central London section to tackle overcrowding. There would now be 24 trains per hour on both central London branches and the northern branches, as well as 30 trains per hour on the Kennington to Morden section between 5pm and 7pm. Battersea extension Throughout the 2000s, no plans were considered for extending the Northern line, as the PPP contracts to upgrade the Underground did not include provision for line extensions. This prolonged period without an extension ultimately changed when the Northern line was extended to serve the redevelopment of Battersea Power Station in 2021. Partially funded by private developers, the £1.2bn project extended the Charing Cross branch of the line for from Kennington to Battersea Power Station, with an intermediate stop at Nine Elms. Approved by Wandsworth Council in 2010 and TfL in 2014, Provision has been made for a future extension to Clapham Junction. ==Services==

Peak As of September 2021, morning peak southbound services are: • 10 tph from Edgware to Battersea Power Station via Charing Cross • 10 tph from Edgware to Morden via Bank • 8 tph from High Barnet to Battersea Power Station via Charing Cross • 8 tph from High Barnet to Morden via Bank • 2 tph from Mill Hill East to Battersea Power Station via Charing Cross • 2 tph from Mill Hill East to Morden via Bank This service pattern provides 16 tph between Finchley Central and High Barnet, 4 tph between Finchley Central and Mill Hill East, and 20 tph everywhere else on the line. Night Since 2016, the Northern line has operated Night Tube services on Friday and Saturday nights between the Edgware and High Barnet termini and Morden via the Charing Cross branch only. Trains run every 15 minutes on each of the northern branches, combining to give eight trains per hour between Camden Town and Morden. There is no Night Tube service on the Mill Hill East, Bank or Battersea branches. • 4 tph from High Barnet to Morden via Charing Cross • 4 tph from Edgware to Morden via Charing Cross ==Map==

Open stations High Barnet branch Edgware branch Camden Town Charing Cross branch Bank branch } ( Trains Gatwick and Luton) || || Metropolitan Railway station opened 10 January 1863. Connects with Circle, Hammersmith & City, Metropolitan, Piccadilly and Victoria lines, National Rail services and Eurostar. Kennington Battersea branch Morden branch Closed stations Permanently closed stations • King William Street (closed 1900; replaced by Bank) • City Road (closed 1922) • South Kentish Town (closed 1924) • North End (also known as "Bull & Bush". Never opened; work stopped 1906) Resited stations • Stockwell – new platforms resited immediately to the south of its predecessor with the 1922–1924 upgrade of the line. • London Bridge – the northbound tunnel and platform converted into a concourse, and a new northbound tunnel and platform built in the late 1990s to increase the platform and circulation areas in preparation for the opening of the Jubilee line. Abandoned plans Northern Heights stations not transferred from LNER • Highgate – High-level only • Stroud Green • Crouch End • Cranley Gardens • Muswell Hill • Alexandra Palace • Mill Hill (The Hale) Bushey Extension stations not constructed • Brockley Hill • Elstree South • Bushey Heath ==Infrastructure==

Rolling stock -bound Northern line train arriving at Finchley Central|alt= When the City & South London Railway opened, it was served by small electric locomotives hauling wooden-bodied coaches. These, however, were deemed underpowered and the coaches had poor interior design, combined with lengthy dwell times at termini for turning the train around. Meanwhile, the "Hampstead Tube" used electric multiple units known as the Gate Stock or later the 1906 Stock. Both of these were replaced by the "Standard Stock", a series of 1920s-built multiple units which also catered for the extension works to Edgware and Morden. As part of the New Works Programme, a total of 1121 cars of 1938 Stock trains were built between 1938 and 1940 to equip the Northern line and its intended extensions with additional capacity, allowing a cascade of Standard Stock trains onto other lines to replace older rolling stock. These were supplemented with identical trailer and non-driving motor cars in 1949 which allowed a reorganisation of formations to ensure seven-car trains were kept throughout the fleet. From the late 1960s, the 1938 Stock began to show reliability issues and long-term industrial action at Acton Works, which supplied the air compressors for them, led to cancellations of up to one-third of Northern line trains and short-formations becoming frequent. In prospect of the Piccadilly line extension to Heathrow Airport and a new fleet of trains for that line (coming in the form of the 1973 Stock), the existing 1956 and 1959 Stock trains were planned to be transferred to the Northern line, with thirty remaining 1938 Stock trains being refurbished to make up the shortfall. However, the relatively short timeframe of rolling stock cascades, owing to the imminent start of the Piccadilly line extension, meant that an equivalent number of new trains were instead ordered based on the Victoria line's 1967 Stock, these becoming known as the 1972 "Mark I" Stock which also entered service that year. The coexisting construction of the Jubilee line also prompted an additional 33 trains of 1972 "Mark II" Stock to run on the Northern line. Transfers of 1956 and 1959 Stock began in 1975 which coincided with the 1972 Mark II Stock being transferred onto the Bakerloo line prior to the Jubilee line's opening in 1979. With the introduction of the first batch of 1983 Stock on the Jubilee line, half of the 1972 Mark II Stock returned to the Northern line to enable the some 1959 Stocks to transfer to the Bakerloo line as a stopgap to replace the final remainder of the 1938 Stock in November 1985. However, resurgence in passenger numbers from the mid-1980s ironically resulted in five 1938 Stock trains to be renovated and returned to service on the Northern line from 1986. The introduction of the second batch of 1983 Stock prompted the transfer of all 1972 Mark II Stocks onto the Bakerloo line which handed the 1959 Stocks back to the Northern line for the final withdrawal of 1938 Stock trains in May 1988. Following the introduction of the 1992 Stock on the Central line, some 1962 Stock trains transferred to the Northern line in 1994 to replace the non-standard 1956 Stock trains. While a new fleet of trains were looked upon by the Underground, budget constraints and the mid-life age of the 1972 Mark I Stock gave way to the idea of retaining and refurbishing the latter while running alongside the new trains. The 1972 Stock began to be refurbished in 1994 to a similar level to those of the Mark II Stock except for the immediate conversion to one-person operation which was expected to occur later. However, only three trains were completed before a Private finance initiative deal between London Underground and Alstom was made for the procurement of 106 new trains coming in the form of the 1995 Stock which eliminated any non-standard fleets. Their introduction began in 1998 and withdrawals of the existing stock took place from that year, with the final "Silver train" being a 1959 Stock train running in service on 27 January 2000. Today, all Northern line trains consist of the 1995 Stock. In common with the other deep-level lines, the trains are the smaller of the two loading gauges used on the system. If the proposed split of the line takes place (initial estimates of 2018 having been abandoned to focus on completion of the Battersea and Nine Elms extension work), 19 new trains will be added to the existing fleet of 106 trains, though additional trains beyond the extra 19 trains may be required to provide a full service for the new Battersea extension. Tunnels Although two other London Underground lines operate fully underground, the Northern line is unusual in that it is a deep-level tube line that serves the outer suburbs of South London yet there is only one station above ground (Morden tube station) while the rest of this part of the line is deep below ground. The short section to Morden depot is also above ground. This is partly because its southern extension into the outer suburbs was not done by taking over an existing surface line as was generally the case with routes such as the Central, Jubilee and Piccadilly lines. Apart from the core central underground tunnels, part of the section between Hendon and Colindale is also underground. As bicycles are not allowed in tunnel sections (even if no station is in that section) as they would hinder evacuation, they are limited to High Barnet – East Finchley, the Mill Hill East branch, Edgware – Colindale and Hendon Central – Golders Green. There are also time-based restrictions for the sections where bicycles are allowed. The tunnel from Morden to East Finchley via Bank, 17 miles 528 yards (27.841 km), was for a time the longest rail tunnel in the world. Other tunnels, including the Channel Tunnel that links the UK and France, are now longer. Depots The Northern line is serviced by four depots. The main one is at Golders Green, adjacent to Golders Green tube station, while the second, at Morden, is south of Morden tube station and is the larger of the two. The other two are at Edgware and Highgate. The Highgate depot is on the former LNER branch to Alexandra Palace. There was originally a depot at Stockwell, but this closed in 1915. There are sidings at High Barnet for stabling trains overnight. ==Potential splitting==

Since the 2000s, TfL has aspired to split the Northern line into two routes. Running trains between all combinations of branches and the two central sections, as at present, means only 24 trains an hour can run through each of the central sections at peak times, because merging trains have to wait for each other at the junctions at Camden Town and Kennington. Completely segregating the routes could allow 36 trains an hour on all parts of the line, increasing capacity by around 25%. The extension to Battersea would allow the Charing Cross branch to terminate at Battersea Power Station. The proposed split of the Northern line would require Camden Town station to be expanded and upgraded, as the station is already severely overcrowded at weekend peak times, and a split would increase the number of passengers wishing to change trains at the station. New redevelopment plans were first announced in 2013 by TfL, which proposed avoiding the existing station entrance and the conservation area by building a second entrance and interchange tunnels to the north, mostly on the site of a subsequently vacated infant school. , TfL said they still "aspire" to split the line. A partial separation was proposed in which all trains from Morden would operate via Bank, while those starting at Kennington (or Battersea) would serve the Charing Cross branch. The High Barnet and Edgware branches would remain served by trains from both routes. ==Incidents and accidents==

In October 2003, a train derailed at Camden Town. Although no one was hurt, points, signals and carriages were damaged. Concern was raised about the safety of the Tube, given the derailment at Chancery Lane earlier in 2003. A joint report by the Underground and its maintenance contractor Tube Lines concluded that poor track geometry was the main cause, and therefore extra friction arising out of striations (scratches) on a newly installed set of points had allowed the leading wheel of the last carriage to climb the rail and derail. The track geometry at the derailment site is a very tight bend and tight tunnel bore, which precludes the normal solution for this sort of geometry of canting the track by raising the height of one rail relative to the other. In August 2010, a defective rail grinding train caused disruption on the Charing Cross branch, after it travelled four miles in 13 minutes without a driver. The train was being towed to the depot after becoming faulty. At Archway station, the defective train became detached and ran driverless until coming to a stop at an incline near Warren Street station. This caused morning rush-hour services to be suspended on this branch. All passenger trains were diverted via the Bank branch, with several not stopping at stations until they were safely on the Bank branch. ==In popular culture==

• In his debut novel Ghostwritten, David Mitchell characterises the Northern line as "the psycho of the family". • The Bloc Party song "Waiting For the 7.18" references the Northern line as "the loudest". • As part of a series of twelve books tied to the twelve lines of the London Underground, A Northern Line Minute focuses on the Northern line. • The New Vaudeville Band's 1967 song "Finchley Central" ("On Tour" in the US) mentions several stations on the line. • The Nick Drake song "Parasite" references the Northern Line. • The 1982 Robyn Hitchcock song "Fifty Two Stations" begins, "There's fifty-two stations on the Northern Line/None of them is yours, one of them is mine." • The 2021 Maisie Peters song "Elvis Song" begins, "Cold bench on a platform/Last train on the Northern Line." ==Maps==

• High Barnet – • Totteridge & Whetstone – • Woodside Park – • West Finchley – • Mill Hill East – • Finchley Central – • East Finchley – • Highgate – • Archway – • Tufnell Park – • Kentish Town – • Edgware – • Burnt Oak – • Colindale – • Hendon Central – • Brent Cross – • Golders Green – • Hampstead – • Belsize Park – • Chalk Farm – • Camden Town – • Mornington Crescent – • Euston – • Warren Street – • Goodge Street – • Tottenham Court Road – • Leicester Square – • Charing Cross – • Embankment – • Waterloo – • King's Cross St Pancras – • Angel – • Old Street – • Moorgate – • Bank-Monument – • London Bridge – • Borough – • Elephant & Castle – • Kennington – • Oval – • Stockwell – • Clapham North – • Clapham Common – • Clapham South – • Balham – • Tooting Bec – • Tooting Broadway – • Colliers Wood – • South Wimbledon – • Morden – • Golders Green depot – • Morden depot – ==See also==