Britain's winter power safety margin falls to a four-year low as data centres and heat pumps drive up demand

The National Energy System Operator forecasts just 5.9GW of spare capacity this winter, 9.5% of demand, down from 6.1GW last year. Under last year's methodology the margin would be only 5.2GW, because the new formula rates wind farms as more reliable. An independent probe found NESO's engineers reported 'high levels of stress and concern' about keeping supply up. NESO still insists the lights will stay on.

Ofgem warned Britain could run out of gas as North Sea reserves and imports fall.

NESO admits 'tight days' are possible and is relying on imports from the Continent.

NESO's Deborah Petterson says households 'can be confident' the grid remains secure.