Thousands of commuters stranded on frozen trains, traffic lights unable to direct, and 1.1 million people left without power marked out an otherwise normal Friday evening in August 2019.
The failure of a gas power plant and an offshore wind farm had led to a power outage, as the UK electricity network failed to handle the sudden imbalance in power being pumped into the system.
It was a rare event, but a stark insight into the problems that could become more regular if the challenge of developing a sustainable energy system is not addressed.
