Tube passengers will be forced to endure a further seven months of disruption as two underground lines are closed for maintenance work.
Metronet has announced the Circle and District Lines will be shut between Earls Court and Whitechapel for 12 weekends between January and July.
This comes as a nine-month project, which began last May, to replace tracks was due to come to an end.
About 2,085 metres of track on the Circle Line has so far been replaced.
Metronet said there may be weekend closures between September and November as well.
Engineers are working to replace ageing track, ballast and sleepers, which is hoped will give passengers a smoother and more reliable service.
The work has been undertaken during 10 weekend closures, but Metronet says more closures are now necessary to complete the project.
Howard Collins, Service Director, from London Underground, said: "The improvements to the tracks are progressing well.
"Real improvements to our service on this section of the District and Circle lines will be achieved when the track replacement is complete and the planned closures mean that this can happen as quickly as possible."
Passengers travelling to Blackfriars, Cannon Street, Mansion House, Sloane Square, St. James's Park, Temple and Tower Hill - stations which are not served by other Tube lines - will be able to use their tickets on London buses.
Extra services will be operating on the Hammersmith & City line during the closures and Hammersmith & City line trains will run to Barking throughout the weekends affected.
The number 15 bus route, which serves the Tower Hill area, will be boosted by extra buses between noon and 1800 GMT on closure days.