London: London's Underground network came to a standstill on Wednesday as its staff began a 24-hour strike in a row over pay and work conditions.
The strike, which officially began at 18:30 BST, affects all Tube lines and finishes at 21:30 BST tomorrow.
London Underground (LU) warned there could be no services tomorrow as a result of the walk-out.
Strikes were called after LU and unions failed to agree a pay deal over new Night Tube services.
Ahead of the walk-out, Mayor of London Boris Johnson tweeted: "Tube strike politically motivated - union bosses need to explain why they refuse to put new offer to members - disgraceful - call it off!"
But the unions involved maintain the new plans would be disruptive to their members' lives.