A fault on the transmission network left large parts of the UK without power this evening (9 August) and the transport system in chaos.
The power cut hit shortly before 5pm as millions of commuters made their way home from work. Many were left stranded at stations and on trains.
National Grid Electricity System Operator (ESO) said the problem was caused by the simultaneous loss of two generators connected to the transmission network, which led to a large drop in frequency.
At one point, the frequency of the power grid, which should be held at a steady 50 hertz, fell to less than 49 hertz.
The ESO responded by disconnecting an “isolated portion” of demand to prevent the frequency from falling further.
The outage affected all six of the distribution network operators in Great Britain. The ESO said power supplies had been fully restored across the entire country by 6.30pm.
Delays and cancellations were reported by a raft of train operators, including Southern Rail, Gatwick Express, Thameslink, East Midlands Trains, Great Northern Trains and London North Eastern Railway. Several companies urged the public to avoid travelling on their services entirely.
There was disruption on the roads too as traffic lights switched off.