Passengers have been warned to avoid using a busy London Underground line for four days while train drivers take part in two 24-hour strikes.
Bakerloo Line drivers walked out at 11:59 GMT and will again on Sunday in a dispute over timetable changes.
Transport for London (TfL) advised commuters to complete all journeys on the line by 12:00, with a full service not expected to resume until Tuesday.
The action is only on one line but engineering works will affect others.
The Rail, Maritime and Transport Workers (RMT) union said it had called the strikes due to "the impact on train drivers over unworkable timetable changes".
"The bottom line is that you cannot place intolerable stress and pressure on Tube drivers that impacts on their safety-critical role," general secretary Mick Cash said.
The two 24-hour strikes meant there was "likely to be little or no service until Monday evening", according to TfL.
Nick Dent, London Underground's director of line operations, apologised for what he called the "unnecessary disruption" caused by the two walk-outs.
"I would urge the RMT to continue working collaboratively with us to resolve these issues," he said.
Engineering works on several other Tube lines will add to disruption in the capital on Saturday and Sunday.
The Circle, District, Hammersmith & City and Metropolitan lines will be closed in central London to test a new signalling system, while the Northern Line will not run between Kennington and Moorgate for work on the Bank Station upgrade.
Details of other engineering works affecting Tube lines over the weekend can be found here.