London Underground staff on the District Line are staging a 24-hour strike amid a row over the treatment of a driver.
Transport for London (TfL) say the driver is said to have been involved in “three” separate safety incidents “within 11 weeks”.
The driver is said to have “mutually” decided to return to a role on a station, but union Aslef dispute this.
Passengers are being warned to expect some delays on the District Line.
London Underground’s Nigel Holness said: “With so many incidents in a short space of time, despite several weeks of training and assistance, it was simply not safe for this employee to continue in a role as a driver.”
TfL say the impact of the strike is “expected to be minimal” in central London, but there will be “more time” between trains on the western branch of the line and east of Tower Hill.
There will be no services to Kensington (Olympia).
Finn Brennan, of Aslef, claimed London Underground bosses “threatened a disciplinary hearing to make the driver ‘agree’ to being redeployed”.
“Instead of recognising the concerns of our members, and reps, management are refusing to acknowledge that they have failed to follow their own procedures and now refuse to talk to this union.”