A number of London Underground stations are closed as Tube workers strike over terms and conditions.
Customer service managers with the Transport Salaried Staffs’ Association (TSSA) are taking part in the industrial action.
The union had warned that stations could close at last minute and by 07:00 BST, seven were marked as closed on Transport for London’s (TfL) website.
TfL said the strike was “disappointing”.
TSSA held a strike earlier this month which the union’s general secretary said “had a real impact”.
The union’s general secretary Maryam Eslamdoust said members had been “forced to take further strike action”.
Following Friday’s strike, there will then be an overtime ban until 5 May.
A TfL spokesperson said: “While we don’t expect this action will cause significant disruption, we urge TSSA to continue to work with us to help find a resolution.”
Customers can check for the latest service updates on the Transport for London website.