Both Boris Johnson and the leader of Southwark Council have this week made positive statements about the prospect of an extension of the Bakerloo line beyond Elephant & Castle.
The Mayor of London has indicated that any tube extension would need to be funded by private development along the route of the line.
"I am committed to carry out a further review of the potential for a southern extension of the Bakerloo line in my transport strategy and I am keen to progress this as quickly as possible," said Boris Johnson this week in response to a written question tabled by the Green Party's Darren Johnson AM.
"TfL has already completed a strategic assessment of a range of potential transport schemes for south-east London.
"The culmination of this work was the South-East London Rail Access Study, which identified a possible corridor for a future extension from Elephant & Castle to Hayes via Lewisham, amongst other schemes, as being the most closely aligned with the objectives of the transport strategy.
"However, further analysis is needed before any firm proposal can be developed and funding would need to be secured for the scheme.
"TfL is doing a piece of work with the London borough of Southwark to look in detail at what development would be needed around the route to both justify the economic case for the extension and fund it."
Southwark Council leader Peter John, who recently secured the support of the Mayor for the extension project during a conversation at a property trade fair on the French Riviera, told council assembly this week that Boris Johnson is "firmly on board".
"We are closer than ever ... to seeing this project become a reality," he said.
"We've got it at last right at the top of the Mayor of London's agenda.
"That's very exciting for the residents of Southwark and very exciting for the residents of Lewisham.
"It would be very exciting for the residents of Bromley but their Conservative leader is utterly opposed to extension of the tube to Bromley.
"He doesn't want to see jobs and growth in his borough. Well shame on him!"