London's population is expected to exceed 10 million in 2030 and TfL says this will increase the strain on already-congested road and rail networks in the southeast of the city, an area not currently served by the tube network due to the density of heavy rail lines.

According to a report published by TfL on December 17 (PDF link), various options have been considered for the extension of the Underground network into southeast London and the link to Lewisham has the strongest business case, with the potential to support the construction of up to 25,000 new homes.

TfL says that if government approval is granted, construction could begin around 2024 and trains could be running to Lewisham by 2030.

More than 15,000 people responded to an initial public consultation in 2014, with 96% in favour of an extension, and a further round of consultations is planned for next year.

TfL says it is looking at funding options for the project, which could include seeking contributions from new residential and commercial developments along the proposed route. This model of funding has already been adopted for the Northern Line extension to Battersea.