In a dispute about driver rotas, London Metro drivers from six Tube lines have gone on strike for 24 hours, according to BBC.
At 04:30 GMT, members of the Rail, Maritime and Transport unions on the Piccadilly, Victoria, Northern, Central, Waterloo & City, and Jubilee lines walked out.
Changes to rotas, according to the union, will devastate members' work-life balance, but transportation executives have branded the walkout "unnecessary action."
TfL (Transport for London) claims to be running over 60% of services.
It's the first time since October 2018 that a strike has spanned multiple Metro lines.
Some portions of the subway network have little or no service, while others are busier than usual.
The strike will also have an impact on the Night Tube's reinstatement, which was set to begin on Sunday for the first time since March last year.
From early in the morning, picket lines were set up outside various Tube stations.
As the strike threatened to bring the city to a halt, several Londoners expressed concerns about transportation.