On 11 November, 2007, Transport for London began to take over operation of several suburban rail services around the periphery of central London, turning them into a unified North London Railway. Once connected with an extended East London Railway from 2011 onwards, the network will provide better services through the city's suburbs, including the vague possibility of something resembling an Orbirail service encircling the capital. This Entry looks at the history of each of the constituents of the London Overground network, and goes into the details of the new system, planned to be mostly completed in time for the 2012 London Olympics. To allow work on the first phase to be completed by 2010, the East London Line will be closed for three years, starting from December 2007.

East London Line

The East London Line opened in 1869, becoming integrated with the rest of the London Underground in 1884 via a spur onto the District line near Aldgate East. The line crosses under the Thames via Brunel's Thames Tunnel, which was constructed between 1825 and 1840. Although the East London line was operated as part of the Metropolitan Railway during the first half of the 20th Century, it became a separate entity in the 1980s, and existed as a short line running from Shoreditch to New Cross and New Cross Gate until 2006. At that point, the building works for the East London Line Extension began, with Shoreditch becoming disused. The first phase of expansion, due to be ready in 2010, will take the line up from Whitechapel to reach a stop at Dalston Junction, which will sit next to the North London Line at Dalston Kingsland, while also being extended over mainline tracks to reach Crystal Palace and West Croydon to the south.

Phase two would then extend the running of the East London Railway from Dalston along the North London line to reach Highbury & Islington on the Victoria line, while another extension onto mainline tracks would be made along an old disused section of railway from Surrey Quays onto the existing South London line towards Clapham Junction. The actual project involves the construction of four new stations and a line between Whitechapel and Dalston, as well as a stop at Surrey Canal Road on a single track spur towards Clapham which will soon be doubled and re-opened. The whole project involves no tunnelling work, and will essentially just be another suburban line. When the first phase of construction has finished, the East London line will lose its Underground status, becoming the East London Railway section of the London Overground.

South London Line

If plans to extend the East London Railway from Surrey Quays to Clapham are given the go-ahead, the Overground will need to take over the inner South London line between Queens Road Peckham and Wandsworth Road. The South London line was originally opened in 1862, with trains running from London Victoria and passing through Battersea, Clapham and Peckham to reach London Bridge station. If current services are cancelled to allow the Overground to run along part of these tracks, then Wandsworth Road and Clapham High Street will be left without any service into central London, while Denmark Hill will lose its connection with London Bridge.

North London Line

The North London line is the next link in the chain of railways which will make up the Overground system, and runs from Richmond in the west to Woolwich in the East, via Hampstead, Highbury and Stratford. The first part of the line opened in 1869 as an extension to what was then called the North London Railway (NLR). The NLR had previously been running between the Isle of Dogs and Camden¹, and the extension added a line from Stratford to Broad Street via Dalston Junction as well as a line from Richmond to Dalston via North London. Broad Street station eventually closed in 1986, leaving the NLR as a line between Stratford and Richmond without a central terminus. Work is currently underway on the disused section between Broad Street and Dalston, which will soon be reopened as part of the East London Railway.

The other part of the North London Line was part of the North Woolwich to Palace Gates line, which ran via Stratford and Seven Sisters to terminate at Palace Gates near Alexandra Palace². The first part of this line opened between Stratford and Canning Town in 1846 on the Eastern Counties & Thames Junction Railway (EC&TJR), with the line being extended to reach North Woolwich a year later. The most southern part of the line was later diverted into a tunnel under the Royal Victoria Dock, as the surface line across this part had to cross a swing bridge over the docks, thus slowing down services. The Docklands Light Railway now runs along a viaduct above the Royal Victoria Dock on its way to King George V, serving much of the same area as the railway line between Canning Town and North Woolwich. In 1963 the northern part of EC&TJR was redirected to terminate at Tottenham Hale, and it was later cut back to Stratford.

In 1979, the CrossTown LinkLine service began to run from North Woolwich to Camden Road via Stratford, making use of the leftovers from both the NLR and the EC&TJR. The two lines were properly merged when Broad Street closed and the line between Dalston and Woolwich was electrified, and the North London Line was formed, first appearing on the London Underground map in 1977. In the early 2000s a service was operated between Ipswich and Basingstoke via the North London Line, but it didn't catch on due to lack of advertising. The line will be run by Silverlink until it is taken over by Transport for London in November 2007, although the section between Stratford and North Woolwich has already been closed to improve running, with the area already being served by the Docklands Light Railway. The DLR is to take over the section from Stratford to Canning Town, terminating at a new stop at Stratford International station, and meanwhile there are plans for Crossrail 1 to take over the now-disused North London Line station at Custom House.

Watford DC Line

This line runs between London Euston and Watford Junction, with its only relationship to the other suburban services being at Willesden Junction, a station which serves both this and the North London Line. In 1837, the first section of what is now the West Coast Main Line opened between Euston and Harrow & Wealdstone, and by 1858 the line had reached Watford Junction. In 1868, a line was opened between Watford Junction and Rickmansworth Church Street, leaving the course of the main line north of Bushey, with a further branch to Croxley being opened in 1912. Although this section closed in 1996, it will soon reopen as the Croxley Rail Link on the Metropolitan line³.

In 1917, the Bakerloo line reached Queen's Park and started to make use of the New Lines constructed by the London and North Western Railway (LNWR) between Queen's Park and Watford Junction parallel to the mainline ones in 1912. These were electrified using a DC third rail/fourth rail system⁴, hence the name 'Watford DC Line' for the modern electrified service. In 1922, local services began to use these tracks, with the Bakerloo line being cut back to Harrow & Wealdstone during the 1980s. The Bakerloo line service along the section between Queen's Park and Harrow & Wealdstone was withdrawn completely between 1982 and 1984, but the service was eventually fully restored in 1989. The DC Line is now shared between the local mainline services and the Bakerloo, though the latter still only runs to Harrow & Wealdstone. The mainline services will be operated by Silverlink until Transport for London take over in November 2007.

Primrose Hill

A link between the North London Line near Camden Road and the Watford DC Line just outside Euston was opened in 1855, calling at a station at Primrose Hill, near Chalk Farm, just before joining the DC Line. The section closed to passenger traffic in 1992 due to a reduction in services across the short line.

West London Line

The West London Line runs from Willesden Junction to Clapham Junction via Kensington Olympia, and will therefore act as a branch off from the course of the North London Line at Willesden Junction, terminating next to the East London Line Extension in Clapham. The first part of the line was built between Wormwood Scrubs and Shepherd's Bush as an atmospheric railway⁵ in 1840, and was soon converted into an ordinary railway. The construction of the West London Line, which would allow trains to pass around central London where overground lines are banned, had earlier been permitted by an Act of Parliament in 1836. The new line was finished in the mid 1860s, and made use of the path of the atmospheric railway for part of the line's length. The line was later electrified using a third rail system. The line crosses the Thames via the Battersea Railway Bridge, and the line is also used by trains heading for Watford Junction from the south. The line will be used by Eurostar trains heading from Waterloo to a depot at the northern end of the West London Line until the Eurostar terminus moves to St Pancras, at which point a new depot at Temple Mills near Stratford will be used.

The line will be operated by Silverlink, who sometimes run trains from the West London line onto the North London line, until Transport for London take over in November, 2007. Work started in 2006 to add a new stop at Shepherd's Bush to provide interchange with the Central line, and the Hammersmith & City line will soon gain a new stop at White City nearby. Another new stop will be constructed at Imperial Wharf near Chelsea Harbour, but meanwhile the planners have so far turned down a proposal by Chelsea Football Club for a stop at Stamford Bridge.

Gospel Oak to Barking Line

The Gospel Oak to Barking Line⁶ begins at Gospel Oak station on the North London line, and then runs eastwards via Blackhorse Road to reach Barking. The history of the line starts with the Tottenham & Hampstead Junction Railway (THJR), opened in 1868 to allow trains to run from Fenchurch Street, through East London, north towards Tottenham and then back in a southwesterly direction to reach a stop at Highgate Road, near the southeast corner of Hampstead Heath. The combination of seemingly the longest route from Central London possible and a terminus with no interchanges available made the line particularly unsuccesful, and it closed in 1870. However, a link was then built to allow trains from Moorgate on what is now the Thameslink line to run onto the THJR just north of Kentish Town. This effectively put the London terminus on the opposite end of the line, with trains now running outwards to Tottenham via a stop at Highgate Road. In 1888, a planned branch to Gospel Oak finally opened, although most trains still went via Kentish Town instead.

The main section of the Gospel Oak to Barking Line was completed in 1894 as the Tottenham & Forest Gate Railway between South Tottenham and Woodgrange Park, built to link the Temple Mills to Seven Sisters line at Tottenham Hale with the Forest Gate and Barking line near Wanstead Park. Trains could then run from the London, Tilbury and Southend Railway at Barking and onto the line towards Forest Gate, leaving the line just before Forest Gate to call at Wanstead Park. This line would then run to South Tottenham, where trains could join the THJR towards Gospel Oak or Kentish Town. Although the Gospel Oak branch and terminus was closed in 1926, it was later reinstated when the through link to Kentish Town was closed as part of the Thameslink project in 1981.

Although the line's popularity dropped during the 1960s and the line fell into disrepair, services continued along the line and have since improved due to the way in which the line now bypasses the centre of London. During its life as a separate entity the line was never electrified, with diesel trains serving the stations, making the line seem like a rural line that had been accidentally dropped into the suburbs of London. The bi-hourly trains were generally unreliable up until 2000, when the old diesels were finally replaced. It is likely that the line will be electrified and the platforms extended to take trains longer than six carriages. However, proper integration with the North London Railway would require rebuilding of the platforms and tracks at Gospel Oak, as although the line is double track and fully linked to the North London Line, the terminus at Gospel Oak consists of a single platform and a small single track siding next to the main platforms on the North London Line. These changes would have to be made carefully as the junction at Gospel Oak is also used by freight trains.

In the future, the line may be extended through Dagenham Dock, where it would interchange with a future Dockland Light Railway extension from Beckton to Dagenham, to reach Rainham. Another possibility would be the re-opening of Junction Road station near Tufnell Park to allow interchange with the Northern Line.

Forming the London Overground

The North London Line, Watford DC Line, West London Line and the Gospel Oak to Barking Line will be combined to form the North London Railway, while the East London line will become the East London Railway. New trains will be provided for the North London Railway in 2009 and for the East London Railway in 2010. The two lines will then be connected via a link in Dalston in February 2011, with part of the South London Line eventually being connected to the East London Railway to form the final London Overground, which should hopefully prove to be the meat on top of the spaghetti that is the London Underground. It would be possible for the lines to form a circular route consisting of the following:

• East London Railway tracks between Clapham Junction and Dalston.

• North London Line tracks between Dalston and Willesden Junction.

• West London Line tracks between Willesden Junction and Clapham Junction.

This sort of plan has been around for some time under the alias of 'Orbirail', but is generally impractical due to the problems it would cause with timing and reliability - just look at the Circle Line. It should be noted that at the time of writing, the East London line extension between Surrey Quays and Clapham Junction is unfunded, and so this part may never actually come into play.

Before plans had been finalised, there was in fact another possible way things could work out, providing another link between the existing lines. In this scenario, the section of the Watford DC line into Euston would have eventually closed, with trains running down from Watford heading onto the Primrose Hill link and onto the North London line. A further possibility was the Bakerloo line taking over most of the local services on the Watford DC Line, with London Overground services terminating at Queen's Park or Willesden Junction. Forgetting about the Watford DC Line for the moment, the following services will probably run once the project is finished:

• Clapham Junction - Willesden Junction - Gospel Oak - Blackhorse Road - Barking

• Richmond - Willesden Junction - Gospel Oak - Camden Road - Canonbury - Stratford

• Queen's Park - Primrose Hill - Camden Road - Canonbury - Stratford

• Caledonian Road & Barnsbury - Canonbury - Shadwell - New Cross

• Caledonian Road & Barnsbury - Canonbury - Shadwell - New Cross Gate - Crystal Palace

• Caledonian Road & Barnsbury - Canonbury - Shadwell - New Cross Gate - West Croydon

• Caledonian Road & Barnsbury - Canonbury - Shadwell - Surrey Canal Road - Clapham Junction

For every train starting at Caledonian Road & Barnsbury there will be another starting at Dalston Junction and heading south. If the lines retain their current layout, then the services on the Watford DC and Gospel Oak to Barking Lines will probably be isolated, with trains on the North London Railway from Richmond and Clapham all running to Stratford via Canonbury. Either way, the stretch between Caledonian Road & Barnsbury and Canonbury looks set to be quite busy in the future.

Running the London Overground

The Oyster Card system, which involves the use of electronic passes which can already be used as tickets and/or season passes on the London Underground, Docklands Light Railway and Croydon Tramlink as well as selected suburban services, will be added to all London Overground stations. The stations will see an increase in staffing and many will have ticket barriers, CCTV cameras and better lighting. The network will be served by Bombardier Electrostar trains, as much of the line is suitable only for third rail mainline trains. The trains will be branded in London Underground colours, while the insides will be very tube-esque with orange hand rails to hold while standing and line maps and electronic information boards sitting just below ceiling height.

Trains could be up to six carriages long and may run up to 16 times per hour on the Caledonian Road & Barnsbury to Surrey Quays section of the East London Railway, although other parts may have only four to eight trains per hour, with just two trains per hour running on the Gospel Oak to Barking line until the project is properly finished. Station fronts and interiors will boast new Overground signs, with the network adopting the orange colour of the East London line to create an orange roundel⁷. On the tube map, the network will appear as a pair of thin parallel orange lines similar to the dark green ones representing the Docklands Light Railway. The system will be separate from the London Underground, although the same fares system will probably be adopted.

Interchanges

Passengers will be able to change to mainline services from a number of Overground stations, including changes to continue journeys from the Overground termini at Watford Junction, Richmond, New Cross, Crystal Palace, West Croydon, Clapham Junction, Stratford and Barking. Clapham Junction provides a link to most of the southwest, with many trains from Waterloo and Victoria stopping there. The Overground links to many of the suburban lines in South London, and Highbury & Islington station provides a link to the mainline out of King's Cross towards the north. Other links include West Hampstead station, which is only 200m away from the Thameslink line towards Bedford, and Shadwell and Stratford, both of which are close to Dockland Light Railway stops of the same name. The Overground has the following links to the London Underground:

• Bakerloo line - every stop between Queen's Park and the northern terminus.

• Central line - Stratford and Shepherd's Bush.

• District line - Barking, Whitechapel, West Brompton, Kensington Olympia, Gunnersbury, Kew Gardens and Richmond.

• Hammersmith & City line - Whitechapel.

• Jubilee line - West Hampstead.

• Northern line - Euston and Clapham Common (for Clapham High Street Overground station).

• Victoria line - Blackhorse Road, Highbury & Islington and Euston.

Construction of interchanges at Tufnell Park on the Northern line and at Brixton on the Victoria line would also be possible. Curiously, the Overground line at Whitechapel will pass underneath the Underground lines there, and passes underneath the Thames as well as crossing it twice via bridges.