[1] An extension southwards from Elephant & Castle was considered as early as 1913, with a formal proposal to extend to Camberwell in the late 1940s.

[2] Since the late 2000s, Transport for London (TfL) has been planning an extension of the line, with a route to Lewisham via Old Kent Road safeguarded in 2021.

[7][8] A large area of South-east London has no rail or tube links, and low public transport accessibility levels.

[12] Furthermore, TfL states that the bus network along the Old Kent Road operates at "close to capacity" with over 60 buses an hour in some sections.

One failed scheme, the New Cross & Waterloo Railway Bill of 1898, had proposed the construction of a line as far south as Old Kent Road, but it was not considered by parliament before it was dropped.

The need to prioritise the extension from Baker Street to Finchley Road to provide relief for the Metropolitan line, financial constraints and the outbreak of the Second World War prevented any work from starting.

Elephant & Castle would not be altered and the additional turn-round capacity would be provided by making Camberwell a three-platform terminus.

The original intention to extend to Camberwell was driven by the wish to serve the area, but in the later scheme operational issues were a major consideration.

In the 1970s, the Greater London Council considered extending the line to Peckham Rye, however this proposal was not taken forward due to high costs, low ridership projections and subsequent poor value for money.

[24] In the early 2000s, Transport for London (TfL) under Mayor Ken Livingstone proposed the Cross River Tram, a new light rail system running south from Kings Cross, Camden and Euston through Central London to Waterloo, with two branches serving Brixton and Peckham.

[37][38] Following the election of Mayor Boris Johnson, the Cross River Tram was cancelled in 2008 due to lack of funding.

A subsequent feasibility report into an extension of the Bakerloo line from Elephant & Castle was commissioned by TfL in 2007, with potential routes south to Camberwell and Streatham, or east to Beckenham and Hayes.

[47] In July 2011, Network Rail published a long-term planning document for London and the South East – the Route Utilisation Strategy (RUS).

[12][48] In January 2012, Network Rail published a summary of its London & South East RUS recommendations, which stated that further feasibility work on an extension was required.

However, Bromley Council called the extension "unacceptable", due to the potential loss of fast trains to London Bridge.

[60] It concluded that an extension towards Lewisham via the Old Kent Road was favoured, as it had the potential of 25,000 new homes along the route – as well as a construction cost £480m less than Option 1b (via Camberwell and Peckham Rye).

[73][74] In February 2017, TfL opened a detailed consultation to examine potential sites for stations and ventilation shafts along the proposed route to Lewisham.

The consultation also stated that expansion and improvement work would be required at the existing Elephant & Castle station, to provide better connections to the Northern line and National Rail services.

This extension would serve development sites along the route, as well as relieving the overcrowded Jubilee line between Canary Wharf and Canada Water.

[91][92][93] Further technical work would take place before a final detailed consultation in 2019, prior to permission to build the extension being sought.

[88] The confirmation of the extension was welcomed by local councils and campaigners, but some residents were disappointed by the lack of a proposed station at Bricklayers Arms.

[95] As well as seeking name suggestions for the two Old Kent Road stations,[96] the consultation included: As with previous consultations, local campaign groups, developers and several local councils supported the extension,[5][100] with Back the Bakerloo urging Prime Minister Boris Johnson to support the extension and contribute to its construction cost.

[105] In September 2019, Sainsbury's and Mount Anvil had submitted a planning application to build 1,161 homes and a new supermarket on the site of the current New Cross Gate Retail Park.

[106] The October 2019 TfL consultation explained that the site was required for construction of the extension, and that other suggested worksite locations were too small or would damage the environment.

[98] After negative feedback from the local community, campaign groups and TfL,[107][108] Sainsbury's and Mount Anvil subsequently withdrew their application in February 2020, stating that the extension had "blighted the site", making their development unfeasible.

[109][108] In January 2020, Southwark Council and TfL both agreed to contribute £7.5m each towards the construction of a new ticket hall at Elephant & Castle, as part of the redevelopment of the shopping centre.

TfL stated that the next step was safeguarding the route, and applying for permission to build the extension via a Transport and Works Act Order, subject to funding being available.

[115][116] In 2021, the route from Elephant & Castle to Lewisham was safeguarded by the Department for Transport, protecting land above and below ground for future construction of the extension.

[118] Due to the financial situations resulting from the COVID-19 pandemic, work to implement the extension was put on hold, with TfL's Comprehensive Spending Review submission stating "we are being realistic about what is affordable over the next decade".

[117] The route of the extension would begin between Lambeth North and Elephant & Castle, as a branch off the existing Bakerloo line tunnels.