MICHAEL Sheen is swapping red carpets for wellies as he investigates claims that toxic “forever chemicals” were dumped in Welsh quarries — and left a legacy locals still fear today.

Buried With Michael Sheen follows the actor and director as he revisits a filmed interview he made nearly a decade ago with environmental campaigner Douglas Gowan, who was terminally ill at the time and wanted to share everything he’d learned after years of trying to raise the alarm. Sheen spent two days questioning Gowan, and that footage has become a key record in a scandal that’s never fully gone away.

At the heart of it are polychlorinated biphenyls (PCBs) — once hailed as miracle chemicals before being recognised as toxic and carcinogenic. From the 1940s to the late 1970s, PCBs were produced at a Monsanto plant in Newport, a city where Sheen spent part of his childhood. The central question: what happened to the factory’s waste?

Gowan believed it ended up buried in landfills across south Wales, in conditions that could have allowed PCBs to seep into surrounding soil and water. Sheen travels to Ynysddu, where two local councillors — both called Jan and nicknamed “the two Jans” — share residents’ memories of lorries arriving at night at a nearby quarry and leaving behind a jelly-like substance on the roads. At a community meeting, locals also describe a grim pattern they think points to something still being wrong: dogs walked in nearby woods repeatedly dying of cancer.

Sheen then heads to Anniston, Alabama, once home to Monsanto’s main PCB factory in the US. A paediatrician there says she’s seen an unusual number of birth defects, including children born without eyes or with their intestines outside their bodies. He also meets attorney Donald Stewart, who sued Monsanto on the town’s behalf in 1993 and secured a $300m settlement — and shows Sheen internal memos dating back to 1949 that, he says, suggest the company knew the risks.

Back in the UK, Sheen digs into Hansard with married investigative duo Dan Ashby and Lucy Taylor, who front the BBC Radio 4 podcast Buried. They point to a 1973 parliamentary attack on Gowan’s credibility following a Sunday Times investigation by journalist Peter Pringle. Sheen also sets out to test soil near the suspected landfill sites alongside an environmental scientist — and a vicar, the Rev Paul Cawthorne, whose interest began with a deathbed confession from a former truck driver who said he hauled barrels of industrial waste.

Buried With Michael Sheen aired on BBC Two and is available on BBC iPlayer.