London Underground drivers have begun the first of two planned 24-hour strikes after last-ditch talks between Transport for London (TfL) and the Rail, Maritime and Transport (RMT) union failed to reach an agreement.
The industrial action started at 00:01 BST on Tuesday and centres on TfL's proposal to introduce a voluntary four-day working week for Tube drivers. The RMT says the plans raise concerns about longer shifts, driver fatigue and reduced flexibility.
Following negotiations facilitated by conciliation service Acas on Monday, the union said TfL had not provided sufficient assurances on key safety and working-condition issues. As a result, the strike is going ahead, with a second 24-hour walkout scheduled for Thursday.
TfL described the action as "bitterly disappointing" and said it had repeatedly assured staff that the proposed changes would remain voluntary. The transport authority aims to operate at least half of Tube services during the strike period.
The disruption is expected to affect large parts of the network. The Circle and Piccadilly lines will not run, while sections of the Metropolitan and Central lines will be suspended. Very limited services are expected before 06:30 and after 21:00.
Buses, the Elizabeth line, London Overground, DLR and tram services will continue operating but are likely to be significantly busier. Passengers are also being warned to expect some disruption on the mornings following each strike day.
The dispute follows earlier strike action in April that caused major disruption across the network. Planned strikes in May were suspended after progress in negotiations, but the latest talks failed to produce a breakthrough.