Slick politicians, money-grabbing businessmen, snooping journalists and a web of subterfuge provide BBC1’s Fields of Gold with all the ingredients of a classic conspiracy thriller.

The story’s bickering protagonists – eager rookie photographer Lucia Merritt (Anna Friel) and bitter tabloid hack Roy Lodge (Phil Davis) – are hot on the heels of a once-in-a-lifetime story.

They are sent to investigate suspicious deaths in a country hospital, something Lodge hopes will prove to be a major exclusive.

Mark Hurst (Max Beesley), the young local farmer who tipped them off, is worried that his sick grandmother might be next. In the meantime, he is reluctantly allowing a biotechnology company to carry out trials of a genetically modified wheat strain in his fields. He always hated how the family had been forced into factory farming; he wants to get back to nature.

Meanwhile, the Minister for the Environment and Countryside, Alan Buckley (James Fleet), is wondering what he’s let himself in for with his new job.

Public concern about foot-and-mouth and BSE may well have subsided, but there are plenty of new problems to take their place. Not least, the Prime Minister appears to hold him personally responsible for keeping a controversial programme of GM crop trials under wraps. The Last thing he needs is a couple of tabloid journalists sniffing around.

Producer Liza Marshall says: “Bubbling underneath the human story are all these issues, such as healthcare, the British farming crisis and our growing unease about disruptions in the food chain.”

“We wanted to tap into a very real fear; to make people think about what they eat. Food will be the issue of the 21^st century – much in the way nuclear power terrified people in the Eighties, GM food has the potential to do the same. You only have to look at the rapid growth of organic products in every supermarket to see people’s unease”.

Anna Friel says a lot of different factors persuaded her to accept this, her first TV role in years. Partly it was Lucia’s personality (“I prefer to play strong-willed , strong-minded women”); partly it was the wide range of issues the script touched on, especially food safety (“I am absolutely passionate about that”); and partly it was the chance to work with Phil Davis at last (“I really admired him before, now he’s one of my favourite leading men. He’s taught me so much”).

But most of all, she smiles, it was the fact that “they let me change Lucia from being posh. I got to use my own accent”.

It seems the 25-year-old actress is a bit fed up with being posh. “I’ve not played a part where I use my own accent for four years”, she explains. “When I first got a draft of the script, Lucia was quite upper-class. I felt she needed more guts and balls to be the one who uncovers the story. The roots of a character are important and being a Northern fighting lass worked much better.”

Friel, who first shot to fame with “that kiss” as Beth Jordache in Brookside, has spent several years away from the TV spotlight. Her last TV role was four years ago in the BBC’s Our Mutual Friend.

Since then, she has wowed the US critics in Patrick Marber’s hit play Closer on Broadway, has received her best British reviews yet for the recent coming-of-age film Me Without You, and seems poised on the brink of Hollywood stardom. Having just missed out on a lead role in Martin Scorsese’s Gangs of New York (to Cameron Diaz), she is currently out in Montreal filming the Hollywood blockbuster Timeline, based on the best-selling novel.

“I just feel more confident these days”, she says thoughtfully. “Especially after the theatre stuff. You learn a lot on the stage, it forces you to break some of those habits you develop in front of the camera”.

Friel certainly has no regrets about returning to small-screen work. “It’s been so great”, she says. “David (Thewlis, her actor boyfriend of 18 months) says he’s never seen me so happy coming home in the evenings from a job”.

Plus she points out, you can’t underestimate the power of TV. “A lot of this drama is inspired by facts that need public attention drawn to them, “ she explains. “And TV is the most powerful communication medium we have. I did loads of research for the part because I wanted to be well-informed about the facts. The more I learn, the more scared I get about how little is being done to fix the damage we’ve done to the food chain.”

In the name of thorough research, Friel also spent a couple of days working with a young female news photographer, most memorably covering South African activist Donald Wood’s funeral alongside a full pack of paparazzi. She fully expected them to turn their lenses on her, and was gob-smacked to find them lending her their stepladders instead.

“They were absolutely great”, she says. “They were just pleased I was doing proper research. It’s made me a bit softer about paparazzi. It’s actually quite a hard job to do”.

Co-writer Ronan Bennett says that the story should ask questions rather than offer solutions. “There are no straight answers about anything. Supporters of GM, for example, see it as a benign and necessary technology that could solve Third World poverty. But its denouncers argue that we don’t know enough about long-term effects yet”.

With so many references, it is difficult to guess what provided the spark of inspiration for the story. Was it the BSE crisis? Foot-and-mouth? The Harold Shipman trial? Or perhaps GM crop saboteurs?

“Actually, it was Day of The Triffids”, ventures co-writer Alan Rusbridger. “I was reading it to my daughter and I thought, hang on, plants mutating out of control? John Wyndham was a Fifties version of an anti-GM campaigner!”.

Annette Brooke