'Millions of litres of oil seeping into UK soil from ageing electricity cables’ 13 August 2025

Electricity companies are leaking millions of litres of oil underground throughout the UK, the Guardian can reveal. In the past 15 years, 3m litres (660,000 gallons) of oil has been spilt under southern England from cables owned by the electricity distribution company UK Power Networks. But leaks are occurring UK-wide; the largest single leak reported in recent years was in Edinburgh, when 24,000 litres was spilt from a ScottishPower Energy Networks (SPEN) cable. The oil is inside ageing electricity cables that were mainly installed in the 1950s to 1970s. It acts as an insulating fluid and helps to keep the cables cool, but as the cables age they leak increasingly. The Energy Networks Association (ENA), which represents the electricity distribution companies, said heavy oil had not been used in new cables for 40 years and many cables had been replaced. UK Power Networks said it had made investments to reduce leakage and was committed to replacing the cables entirely in the long term.

…He said the leaks presented a “huge problem for the environment” and were slowly contributing to major biodiversity loss over long periods of time. Basu visited one site in Norfolk where a cable was leaking oil continuously and had saturated the soil. The oil had seeped into the bodies of trees via the roots, then damaged leaves and caused them to become yellowish in colour and develop spots. The oil-soaked soil had to be removed and replaced with fresh soil. But no one knew “how much of the fluid the rainwater took with it – that was anyone’s guess”, Basu said. Usually an underground oil leak caused no immediate danger, Basu said; it was rarely the case that “this night there was a leak and tomorrow it was a disaster zone”. But with time the oil travelled through the soil into the nearest water bodies including rivers, lakes or the sea, killing useful fungi, bacteria, fish and other aquatic life.

…Companies and regulators do not publish information about precisely where leaks have occurred or oil-filled cables are located, though freedom of information requests from environmental regulators reveal leaks have happened underneath cities, residential areas, riverbeds and arable fields. Lily-Rose Ellis, a campaigner at Greenpeace UK, said: “This is really concerning and is yet more evidence of the urgent need to update our crumbling energy infrastructure. “These cables are at best outdated, but some are virtually antiques and are urgently in need of replacement. The UK electricity grid was designed and built for the energy system of the last century.” …A spokesperson for ENA said the electricity distribution companies had not used heavy oil in newly laid fluid-filled cables for about 40 years and now used biodegradable substances, solid insulation and sealed cabling. It said 310 miles of older cables had been replaced in the past 10 years, and oil-filled cables made up less than 1% of the grid around London and the south-east.