Innocent 2 writer Chris Lang explains why viewers will know Katherine Kelly's character is not guilty from the start

In the standalone second season, Kelly leads the Innocent cast playing former secondary-school teacher Sally, who is imprisoned for supposedly having an affair with and later murdering one of her students, Matty Taylor.

However, we know from the very start of the series that she cannot have committed the murder – she's released five years into her sentence after a new piece of evidence emerges, clearing her name.

Speaking to RadioTimes.com and other press, Lang explained why he wanted to "eliminate the potential of her [Sally] being guilty really early on".

"That was a very deliberate choice, right at the beginning, because you don't want to repeat [yourself], you know, when you're doing a show like this... it's a formatted show that has very specific things that are similar, but the content within it has to be very different. A phrase I use on Unforgotten is "the same but different", which is, you know, you give the audience what clearly appealed, but then you change everything else, all of the content of the story, and it felt like that was one of the things we should do, we should eliminate the potential of her being guilty really early on."

He added that he wanted to "tap in to a similar kind of visceral sense of dislocation that I think we captured, or Lee Ingleby captured, in the first series".

While the focus of David Collins' journey was "what is it like to lose that connection with your children," for Sally in season two, it's the loss of her ex-husband, Sam, with whom she had a stable marriage prior to the scandal.

"We wanted to find something that was similar and as emotionally compelling. And we wanted to mix it up and tell a story from the point of view of a female protagonist. And we settled on the notion of, you know, losing the love of your life, even though they're alive and well, and they're living in the community that you grew up in. Because it felt like such an astonishingly powerful emotional loss when you've done nothing wrong, when you've committed no crime or sin at all. And it's sort of tapped into some yeah, I think, very primal fears," Lang explained.

Speaking about her character, Katherine Kelly added that she worked hard to convey the impact that five years in prison has had on Sally Wright.

"As Chris mentioned, at the very beginning, you find out that that Sally is innocent within the first kind of five minutes," she said, "and what I love about Sally's character is she's very, very forward thinking, she doesn't really talk much about what happened [in prison] unless she's pushed. She wants very much to get her life back. And I really felt that, because she wasn't talking about it very much, that the audience really had to feel and believe at all times that that human being has been five years in prison. And so a lot of my prep was research about that, actually, because I felt that you had to really feel that weight on her."

Innocent series two is coming soon to ITV. Find out where the new season of Innocent is filmed. While you’re waiting, visit our TV Guide to see what’s on tonight, or visit our dedicated Drama hub for all the latest news.