Interview: Julie Walters talks to us about upcoming C4 drama National Treasure

"It keeps me sane, to not live in London, to not be around it too much," she said.

"I don't go to premieres and things unless it's my own one. I'm not interested in being photographed. There's enough publicity around the jobs that you do."

But the perils of living in the public eye are the subject of the 66-year-old's latest work, National Treasure.

The Channel Four drama tells the story of Paul Finchley, played by Robbie Coltrane, a respected family comedian and quizmaster whose life is turned upside down when he is accused of raping a woman in the 1990s.

Inspired by Operation Yewtree, the police investigation into the sexual abuse perpetrated by Jimmy Savile and allegations against other media personalities, the four-parter focuses on the impact of the scandal on Finchley and his family.

Walters, who grew up in Smethwick in the West Midlands, plays his wife Marie, while his daughter Dee is played by Andrea Riseborough.

Marie stays loyal to her husband, despite the fact that he has been unfaithful on numerous occasions, a decision Walters says she understood from the first moment she read writer Jack Thorne's script. "It's about faith and needing to believe certain things," Walters said.

"And as she's a Catholic, she won't want her marriage to be over, despite his infidelities.

"It's about forgiveness and trust, believing him when he says 'I will always tell you what's happening'.

"So those things had to be worked out, why is this woman where she is?

"It's like when you see pictures of Rolf Harris and his wife, it's her that I'm actually fascinated by. How is she standing next to him, holding his arm, in this?"

Despite the sensitive nature of National Treasure's subject matter, Walters says she had no misgivings about taking the role because 'there is a truth behind it'.

It's not sensationalising the issue for the wrong reasons," she said. "It's being done for the right reasons.

"It's about family, that's what is fascinating. It is how you respond to one another and emotionally how you do with one another.

"You do look at these cases and you think 'gosh, I want to know about her'."

On the subject matter, Walters acknowledged: "It's been a really significant part of current affairs recently. We see what's in the newspapers when something like it breaks, but this goes behind the scenes and tells the human side of the story. It shows how relationships are affected."

The show thrives on ambiguity, leaving the viewer constantly questioning whether Finchley is guilty or innocent.

Walters says she sympathises with people who are accused of doing something they haven't done, and are plunged into the media spotlight as a result.

National Treasure examines the contentious issue of 'fishing' – the practice of leaking the name of an accused celebrity to the media in the hope that others claiming to be victims will come forward, strengthening the police case as a result.

Sir Cliff Richard, radio presenter Paul Gambaccini and MP Nigel Evans recently launched a campaign calling for those accused of sex crimes to be given anonymity until they are charged.

"It's very difficult to get rid of that sort of thing," she said. "No matter what happens, some people will always think 'There's no smoke without fire'.

"That is very difficult. On the other hand, as is shown in the series, it really helps the police when things are publicised, because it tends to give other people the courage to come forward, and they can then build a case. And I think that overall, the victim has to come first, no matter what."

Walters says the chance to work with director Mark Munden was one of the main reasons she was attracted to the role, while Coltrane was another big draw. The pair have worked together before on the Harry Potter films, although Walters says they have filmed 'maybe one scene together in 10 years'. But she also admitted she was drawn in by the dark subject matter, which she says writer Thorne had approached 'in a really interesting way'.

"I don't get a lot of stuff like this, I have to say," she said. "It's unusual. It's fascinating – you can't help but be drawn in.

"How do people deal with this? Thorne said the responsibility was 'massive' when it came to getting the right tone.

"The idea that we might get it wrong felt very dangerous because so many people have been damaged by this stuff," he said.

Speaking about Savile, he said: "The fact that we let not just an evil man but an actual monster onto our television sets for that amount of time and then discovered what he was so late on . . . that seems to have affected us all I think and at least is partially responsible for the cynicism with which we now look at the world."

The writer's extensive research for the series included interviews with police officers who had worked on investigations of celebrities suspected of historical sex abuse.

Coltrane has also spoken about Savile, revealing he never met him and never wanted to meet him, because he thought he was a 'creepy wee s---ebag'.

The 66-year-old says that people accused of sex crimes should be given anonymity because of the need to protect victims, even though innocent people can 'lose their lives' over false claims.

He argues that National Treasure is about far more than Finchley's guilt or innocence.

"Episode one is not even about whether he did it or didn't do it," Coltrane explained.

"That's hardly mentioned. What it's about is: what would it be like, for any one of us, if somebody came to the door and accused you of raping somebody 20 years ago?

"Your life literally falls off a cliff, whether you did it or not."

National Treasure starts on September 20, 9pm, on Channel Four.

By Peter Madeley