Black Sky Blackouts: How Prepared Is the UK for a Total Grid Failure?

On the night of Saturday 5 December 2015, Roger Kemp was halfway through a Scandi crime drama when his lights went out. The professor of engineering at Lancaster University, who specialises in safety and electrical systems, looked outside and saw that the sodium glow normally visible over the horizon from Morecambe had vanished. The next day he went for a walk and found a town in disarray. He described people hunting for phone reception and a huge queue at the one working telephone box, and said it was almost like a zombie movie.

The cause was the River Lune, which runs through Lancaster. At 22:45 it flooded, and electricity to 61,500 people in the city was lost. Households had no light or heat, and some water supplies began to fail because they depended on electric pumps. The railway station closed, as did petrol stations and shops. Most cash machines stopped working, and traffic lights failed.

Only two communication systems survived: copper-wire landline telephones and FM radio. The local commercial station The Bay had an emergency generator and one landline, and it sent a reporter outside the affected area to ring in with information. Three months later Kemp gathered people to examine what had gone wrong. The resulting report observed that in a society so committed to digital infrastructure, the most reliable source of news was a commercial station using technology familiar to the engineers of the 1960s pirate ship Radio Caroline.

For Kemp and others in civil contingency, Lancaster was a warning, and this kind of prolonged disruption has a name: a Black Sky event. At a recent summit on UK resilience, discussion centred on the country being able to withstand one for at least 72 hours. A phrase often heard in the field is that we are nine meals from anarchy, reflecting the fear that three days without food could turn a crisis into chaos. The government's "Be Prepared" campaign encourages households to hold their own supplies, though it says there is no specific threat to the grid. Recent events, including the April 2025 blackout across Spain, Portugal and south-western France, have pushed the issue up the agenda.

The BBC has its own Black Sky plan, known in full to only a small number of staff. From what the reporter gleaned, about 100 people would run a special emergency radio studio with secure communication lines that do not rely on the internet, plus fuel, water and food to operate for at least three days without resupply. It would broadcast pre-arranged government messaging, with scripts already published online, covering how much people should drink each day and how to dispose of toilet waste without flushing. Other information would come from a select number of journalists at emergency centres around the UK, using satellite vehicles for as long as diesel lasts.

Broadcasts would travel through radio transmission towers isolated from the internet, with diesel tanks holding between five and 40,000 litres (8,800 gallons) to run generators for three days, because FM is power hungry. Teams would use satellite phones, with pre-agreed protocols and meeting points if those fail. FM was chosen because it works almost everywhere, even in a blackout or a crippling cyber-attack. One BBC insider said planning had originally assumed five to seven days, but the latest advice from the National Energy System Operator, Neso, is that power could probably return in two to three days.

Lord Harris, chair of the National Preparedness Commission, stresses that a power cut means far more than lost lighting. Water supply would likely stop unless a home sits downstream of a reservoir, and sewage tends to solidify without moving water, causing blockages and backing up. He argues that five decades of pursuing efficiency have stripped out backups, pointing to emergency services moving from radio to mobile network technology, so that a mobile outage would also hit their communications. The government insists that moving to 4G and 5G is resilient and reliable. It is also spending £70m on High Altitude Pseudo-Satellites, planes that could circle over the UK and supply at least a week of emergency mobile and internet connectivity. Rico Chandra of Enduring Atmospheric Platforms, the developer, noted that satellites have limits as a fallback when ground networks fail.

The timing is awkward. The copper landline network, which works in a power cut, is due to be switched off on 31 January 2027, and FM radio's future is under government review. The government says copper had been a useful fallback but is now unreliable and hard to repair. Asked whether his report had improved readiness, Kemp paused, then said that if anything the country has gone backwards, and that the switch-off shows no thought about communicating once power is gone. The reporter, meanwhile, lost power on his street last Saturday while writing, and found leaking torch batteries, buried candles and a missing wind-up radio.