2003 London blackout

The 2003 London blackout was a major power outage that occurred in parts of south London and north-west Kent in England on 28 August 2003. It was the largest blackout in South East England since the Great storm of 1987, affecting over 500,000 people.
It was first reported power had went down at 18:15 British Summer Time. Power returned about 34 minutes later and some trains started operating again, but is reported to have taken about two hours to come back to working again in some areas. By 7pm, most trains started running again.
National Grid would say the problem was because of a failed machine at a Hurst building in South East London that helped with power, which caused some alarms.
The tube.
The blackout caused tube trains to stop. It also caused about 17,000 people to be stuck, with computers not knowing where the Tube trains were, which was dangerous. By the next day, the Tube started mostly going on as before again.