“We’re aware of a power cut affecting a large area of London and South East. We believe this is due to a failure to National Grid’s network, which is affecting our customers,” UK Power Networks tweeted.
The brief power interruption caused disruptions to a large number of train services, with some traffic lights also shutting down.
Transport authorities however confirmed that power had been restored and normal service was expected to resume shortly.
In the period when power was out, police officers were deployed to help guide traffic on the roads in order to avoid congestions.
Tens of thousands of homes across swathes of London and the South East were affected by the power cut.