New grid rules that came into effect this week give Great Britain's electricity system operator, Neso, the power to impose short-notice rolling blackouts as a last resort to prevent a total grid collapse, without needing the government to invoke emergency powers. This is significant because it is the first time such large-scale power cuts could be triggered without ministerial involvement, and it comes weeks after whistleblowers accused Neso leaders of downplaying blackout risks during a summer heatwave.

Under the changes, quietly approved by the regulator Ofgem last month, Neso could order disconnections cutting electricity use by more than a fifth in a designated area with just eight hours' notice, resulting in rotating three-hour blackouts nationwide. The measure is designed to bridge the gap between Neso's existing but rarely used local power-cut powers (last invoked during the 1970s miners' strikes) and the government's more sweeping electricity supply emergency code, which has never been triggered and would affect 90% of users over a prolonged disruption. Neso says the new tool would only be used in "the most extreme and unlikely circumstances" after all other options are exhausted, with hospitals, water treatment sites and national security facilities protected from cuts; officials cite the Spain and Portugal blackouts last summer, where full restoration took up to a week, as the scenario this is meant to avoid.