What happens if all the lights go out? This is the plan for a 'Black Sky' event

A “Black Sky” event is a prolonged power failure that disables far more than lighting: water and sewage systems, transport, shops, cash machines and communications can all depend on electricity. Lancaster’s 2015 flood-driven outage left 61,500 people without power; water supplies faltered, the railway and petrol stations closed, and most cash machines failed. FM radio and copper-wire landlines were among the few communication systems that continued working. The experience prompted engineers to warn that a highly connected society can be especially vulnerable when its infrastructure fails. UK resilience discussions now focus on coping for at least 72 hours, while the government’s Be Ready campaign encourages households to keep emergency supplies.

The BBC’s contingency plan would put about 100 staff in a dedicated radio studio with secure communications, provisions and fuel for three days. FM transmitters, powered by diesel generators, would carry government advice and reporting from emergency centres; guidance includes drinking water and handling toilet waste. Experts warn that power loss can disrupt water pumping and sewage, while modernising systems may remove useful backups. Plans for emergency phone and internet coverage using high-altitude aircraft are in development, but copper landlines are due to be switched off in 2027 and FM’s future is under review. The government says the electricity system is highly resilient and has never suffered a total outage, yet one engineer argues preparedness has weakened as old communication options disappear.