Established in 2007 to take over Silverlink Metro routes, it now serves a large part of Greater London as well as Hertfordshire, with 113 stations on the six lines that make up the network.

The Overground forms part of the United Kingdom's National Rail network but it is under the concession control and branding of Transport for London (TfL).

TfL previously assigned orange as a mode-specific colour for the Overground in branding and publicity including the roundel, on the Tube map, trains and stations.

In 2024, each of the six Overground lines were given distinct colours and names – Lioness, Mildmay, Windrush, Weaver, Suffragette, and Liberty – which are intended to reference London's diverse history and communities.

However, the Wilson government's continuing antipathy to the railways,[citation needed] along with British Rail's management's lack of interest in minor local train services, meant that few of these initiatives were carried forward.

The closure process was convoluted because of problems in making alternative arrangements for the North London line, and the remaining services operating from Watford Junction to the City.

The pamphlets and briefings, first issued in 1997, initially suggested a route from Clapham Junction to the Greenwich Peninsula, intended to improve access from south London to the Millennium Dome.

[13] A result of this consultation was agreement by the Secretary of State for Transport, Alistair Darling, to transfer the Silverlink Metro services from DfT to TfL control.

[22] On 25 June 2007, a statutory instrument was laid before parliament to exclude the ex-Silverlink metro lines from the franchising process, which enabled them to be operated as a concession.

[26] The following day there was an official launch ceremony at Hampstead Heath station with the Mayor of London, Ken Livingstone; there was also a later media event on the bay platform at Willesden Junction.

The extension uses an alignment between Surrey Quays and just north of Queen's Road Peckham that had been disused since 1911; new track was laid after some major civil engineering works.

[46] The new London Overground line names and colours were introduced across the London rail network in November 2024 As of December 2024[update], the typical off-peak service pattern is:[47] Battersea Park railway station is served by an infrequent parliamentary train service from Dalston Junction, which terminates at Battersea Park instead of Clapham Junction.

Rolling stock is maintained at Willesden Junction and New Cross Gate TMDs, the latter being newly built for the extended East London line.

Unlike other National Rail operators under the franchise control of the Department for Transport, TfL sets fares, procures rolling stock and decides service levels.

In April 2015, TfL placed a notice in the Official Journal of the European Union, inviting expressions of interest in operating the next concession.

[51] In July 2015, TfL announced the shortlisted bidders for the next concession were Arriva UK Trains, ComfortDelGro, a Keolis/Go-Ahead joint venture and MTR Corporation.

As part of an effort to improve safety and protect revenue, TfL has announced that it will introduce ticket barriers at a number of stations.

[58] TfL, in conjunction with the Massachusetts Institute of Technology, has investigated the use of data from the Oyster smartcard ticketing system to measure the performance of the Overground explicitly from the passenger perspective.

[67] In August 2023, a consultation was announced to provide more clarity to the London Overground network by giving each route its own name and colour on the Tube map, making it easier for passengers to navigate their way around the system.

[72][73] Now called Lioness, Mildmay, Windrush, Weaver, Suffragette, and Liberty, the lines are intended to reference London's diverse history and communities.

The transfer of some suburban services from Liverpool Street in May 2015 from the Greater Anglia franchise to London Overground also distorted numbers, contributing to a very large growth between 2014/15 and 2015/16.

The ends of each Class 378 unit are painted yellow to comply with the National Rail standards that existed when the first wave of new trains began to enter service in 2009.

Similarly, since the takeover of the Lea Valley lines, Overground services are being run with trains inherited from Abellio Greater Anglia which are mostly in a plain white livery with red doors.

Prior to replacement of this rolling stock, the trains were repainted with full Overground livery and the interiors refurbished with Wallace Sewell upholstery and TfL standard signage and route maps.

[98] It was announced in June 2013 that £115 million of funding for electrification was being made available as part of upgrades to rail infrastructure included in the government's 2013 spending round.

[101] Part closures (on weekends and from South Tottenham to Barking) were planned from June to late September 2016, followed by a full closure from October to February 2017,[102] and further evening and weekend works until late June 2017, and finally around four months of further work to add the wires so that electric Class 710 trains can run from early 2018.

[111] Had this change taken place, Kilburn High Road and South Hampstead would no longer have had direct services to Euston station, hindering access to central London.

[121] In February 2024, a public consultation began on a DLR extension to Thamesmead from Gallions Reach, which had been favoured over the previous London Overground proposal due to cost and service frequency.

Under this scheme, TfL would take over rail services out of London Victoria, Charing Cross and Cannon Street to Dartford, Sevenoaks, Orpington and Hayes, but this was rejected following spending cuts imposed by the 2013 United Kingdom budget.

[132] Proposals to reopen the Dudding Hill line to passenger services as part of the London Overground have been mooted for several years.