London Underground services are suffering severe disruption due to “power supply problems”, Transport for London (TfL) said.
The issue means no trains are running on the entire Victoria line.
The Piccadilly line is suspended between Hyde Park Corner and Cockfosters, with severe delays on the rest of the line.
Tube stations were evacuated and closed due to the problem.
The disruption comes as TfL is warning that some of its services will be busier than normal with many people visiting London to pay their respects and attend ceremonial and commemorative events following the death of the Queen.
