National Grid said it was caused by issues with two power generators but the problem was now resolved.

Blackouts were reported across the South East, South West and North East of England, the Midlands and Wales.

Trains were delayed and cancelled, and traffic lights in parts of London stopped working.

The Department for Transport, said: "Today's power outage has had knock on impacts on travel.

"We're working hard with Network Rail and others to ensure systems are up and running as quickly as possible, so that everyone can complete their journeys safely."

At the height of the Friday rush hour, all trains out of King's Cross were suspended.

Passenger Zoe Hebblethwaite said the situation outside of the station was "absolute mayhem" and that passengers "couldn't find an assistant to speak to".