What is a 'Black Sky event'? The UK warning, and the one thing every home should have

What is being shared

The BBC’s long read by David Sillito, published on 7 November, is headlined "What happens if all the lights go out? This is the plan for a ‘Black Sky’ event". It recalls the Lancaster flood of December 2015, when 61,500 people lost power, describes the BBC’s plan to keep broadcasting on FM, and says "the government says there is no specific threat to the grid".

LADbible followed that afternoon with "UK ‘black sky event’ warning as expert explains item every household should have", by James Holt. It quotes Andrew White, described by LADbible as "CEO and Telecommunications and Data Centre Expert at Harberry Limited": a black sky event is "a catastrophic, long-duration failure of critical national infrastructure, especially the electric grid, lasting weeks or months". That is his definition, not an official one. The item is a wind-up FM radio; the rest restates the BBC.

What a Black Sky event actually is

"Black Sky" is not an official UK term and has no statutory definition; the National Risk Register 2026 does not use it. Civil-contingency planners and the BBC use it for a long, wide loss of power that takes connected services with it. The one-word "BlackSky" is a page-title artefact, not the name of a government plan for the internet.

The official version is the "National power outage" scenario in the latest National Risk Register (2026): a failure of the National Electricity Transmission System. It says "Great Britain has never experienced a nationwide loss of power and the likelihood is low". Its reasonable worst case is a total failure in winter with "secondary impacts across critical utilities networks (including mobile and internet telecommunications, water, sewage, fuel and gas)". A recent resilience summit, the BBC reports, discussed withstanding one for "a minimum of 72 hours": Be Ready’s three days.

Has it ever happened?

Not across Great Britain. The Register says so, and the Cabinet Office told the BBC there has "never been a complete outage in the grid’s 75-year history".

The nearest was 9 August 2019, when more than a million customers lost supply after a lightning strike was followed by the loss of two large generators. Automatic protection cut about 4% of national demand and all supplies were back within 45 minutes, Ofgem’s report shows. The big outages people remember are regional and weather-driven: Storm Darragh in winter 2024–25 left more than 2 million homes without power, and Lancaster’s 2015 flood cut 61,500 people off.

Abroad, the closest example is the Iberian blackout of 28 April 2025 in mainland Spain and Portugal, with brief disruption in a small area of south-west France. ENTSO-E’s final report on 20 March 2026 found "a combination of many interacting factors, including oscillations, gaps in voltage and reactive power control".

How power would come back

NESO, the National Energy System Operator, has an Electricity System Restoration Standard in its licence, set by the government in 2021 and written into its licence by Ofgem that August: 60% of each region’s demand restored within 24 hours of a total shutdown and 100% of Great Britain’s within five days, with full compliance required by 31 December 2026. These are targets from the end of this year, not a measure of what the system could do today.

The Register’s 2026 edition gives the planning picture for its worst case: some consumers gradually reconnected within a few hours, about 60% of demand back within two days, all customers by days five and six with controlled cuts at peak times, and full, stable power beyond seven days. The BBC quotes an unnamed insider saying NESO’s latest advice is "two to three days"; that is a conversation, not a NESO publication. White’s "weeks or months" is longer than this, though the Register’s cyber-attack scenario says full restoration "could take at least 7 days" and critical services "may take several months".

Why everyone is saying ‘get a radio’

It comes from Lancaster: "The two communication systems that survived were copper wire landline telephones and FM radio." The BBC describes its own plan: an emergency radio studio, secure lines that do not depend on the internet, three days of fuel, water and food, pre-arranged government scripts, and FM transmitters with diesel for three days. "Why FM? Because it works almost everywhere, even in a blackout or a crippling cyber-attack."

None of this is new for households. The Be Ready checklist already lists an "FM radio (battery/wind-up)" beside the torch and power bank, so LADbible’s must-have is the government’s own list. We have compared wind-up radios and battery radios. Sillito found his torch batteries had leaked and his wind-up radio missing. Check yours.

What to do now

Follow the Be Ready checklist: "being ready for 3 days helps you manage while support reaches those most in need". Bottled water at "3 litres per person per day for drinking"; non-perishable food for three days; a torch and spare batteries; an FM radio; a charged power bank; cash in coins and notes, and cards; copies of documents; and important phone numbers and medication doses written down. Add blankets and first aid, and check it every six months. The checklist, item by item goes through them.

Write 105, the free power-cut number in England, Scotland and Wales (03457 643643 in Northern Ireland), on paper. If anyone at home has extra needs (powered medical equipment, state pension age, a child under five and more), join the free Priority Services Register for advance warning of planned cuts and priority support. In a national outage no home's supply can be prioritised, the Register says, but responders would use the PSR to target help. Our national power outage guide has the fuller picture.

What not to do

Don’t panic-buy. Nothing in either article or from the government asks households to stock more than the Be Ready three days, built up gradually.

Don’t leave candles burning; Be Ready’s power-cut advice is that a torch is safer. Never run a generator, camping stove or barbecue indoors or in a garage: the NHS lists all three as carbon monoxide risks.

Watch for scams that borrow the headline: treat any text, email or doorstep call about "the black sky event" that wants a payment or a login as a scam until checked another way. And don’t read one commentator’s "weeks or months" as the plan: the Register’s figure is full, stable power beyond seven days, and NESO’s target is five.