Scruffy Sheen turns into Shoestring to probe Wales's toxic waste scandal: CHRISTOPHER STEVENS

Buried With Michael Sheen (BBC2)

Rating: Two stars out of five 

The scruffiest detective ever seen on telly, more disreputable than Columbo in his mac, more dishevelled than Morse in his beer-stained suit, was Eddie Shoestring.

Long-haired, unshaven, with his tie looped round his neck like a noose, he was portrayed by Trevor Eve in a popular but short-lived 1979 detective drama co-written by Bergerac creator Robert Banks Stewart. 

My guess is that Michael Sheen, who would have been about ten, was a fan.

The Welsh actor certainly seemed to be modelling himself on Eddie S as he played private eye in the two-part documentary Buried, probing the threat of chemical waste leaching from underground dumps into the water supply.

In a checked shirt, with a salt-and-pepper beard that seemed to moult and regrow from one shot to the next, Sheen schlepped around Wales and over the border into Cheshire, visiting communities blighted by toxic waste.

He then flew to the US, to hear parallel horror stories.

His sincerity seemed beyond doubt, but quite how he became involved was a bit of a mystery.

'About ten years ago,' he said, 'I just had a lot of time on my hands and I found myself scrolling through a few things and stumbled across this story of a man who claimed that the people of Wales were being poisoned.'

The man was National Farmers' Union environmentalist Douglas Gowan. 

Sheen, who lived in Los Angeles at the time, contacted him and, in 2018, spent a weekend with him, recording a seven-hour interview about his work. Gowan was seriously ill and died a few weeks later.

If it seems bizarre that one of the most sought-after actors in the world should take time off for a spot of investigative journalism, it's even harder to understand why he's taken so long to follow it up.

We found him in a wooden cabin in the Neath Valleys, rewatching video of his meeting with Gowan on an old-fashioned projector, with a pull-down screen - the way families used to watch cine film of their holidays. 

The pine planks of the walls were plastered with maps, documents and Post-it notes.

This, traditionally, is how oddball sleuths track serial killers, and all the evidence suggests that banned PCB chemical waste dumped in old quarries across Wales could pose a bigger hazard than any mass murderer.

PCBs are known as 'the Godfather of Forever Chemicals', because they never dissipate. We heard of children suffering scabs on their legs after paddling in contaminated water, waves of tumours killing dogs that were exercised near the dumps, and a farmer who died from blood cancer.

Proving with certainty that the chemicals were to blame was impossible - but tests showed the late farmer's land registered PCB levels 2,000 times greater than average. 

This news deserves to be much more widely known - but Sheen's involvement is more a distraction than a publicity boost.