Can you explain the idea behind The Shadow Line?
"It is one murder, investigated by both sides of the line, cops and criminals. It looks at the methods that they use to pursue the result. But whenever you have a line, what interested me most, was its morality. If you are going to do something, how far will you go to do it. How far will you push that line of your own personal morality and when you will cross it? That's the central idea of the show."
After watching the first episode it is hard to decide who are the good people and who are the bad...
"That's the issue of the morality. As soon as you go the other side of the line, there is a criminal, who in the first episode is the most empathetic character. There is a copper, played by Chiwetel Ejiofor, who you think will bring the moral imperative, but in fact he has an unsure past. That blurring of the lines is what's attractive. It doesn't engage with you to offer you an easy solution. You won't be able to make your mind up or quite know right until the very end."
Were you aware of the large number of police dramas being made at the moment?
"I'm sure that's true and you pay attention to that, but this is a story that evolves. It starts as a police procedural, quite quickly gets rid of that - our interest was not of the police side - it quickly develops into a crime drama and then it evolves further into a spy thriller or a conspiracy thriller. It's constantly changing and the tools we use to keep the audience's attention with gripping ideas change as well. It wasn't something where we just said, this is a crime thriller."
You worked as producer and writer. Does that make it an easier job or a harder one?
"When making a production of any size, and this is quite a large one, the important thing is to be sure your choices at the front-end are the correct ones. That's 90% of the job. The rest of it when you have made those choices is collaboration. It is like sending 200 people into the wilderness. You are outside of your normal terrain with 200 people gathered to hit a nail at the same time, synchronised. In order to do that, we have to feel that we're hitting the same nail and how we're doing it. That decision comes at the front-end. The rest is simple, you collaborate. You midwife the project, that's the best I can do. I don't say, that's the baby. We can only make the baby together."
Did you feel in any way restricted when making this series because it was for BBC Two?
"I don't think an audience wants you to do that. I think then you are guessing what they want and you are doing the thinking for them. What I try and do is create an argument, an argument that needs to be resolved. The argument needs to be gripping and compelling enough that an audience will want to engage in it as well. But the argument can be complex, I think it should be complex and I don't think you should be thinking that you are making something for BBC Two."
What was the inspiration for this series?
"I love the '70s American conspiracy thrillers because they are a very rare time in that they were post-Nixon and pre-Reagan. The construction of the stories were always quite mainstream and they weren't rarefied, with people like Robert Redford or Warren Beatty. They were mainstream characters and very accessible thrillers, but we are discovering very striking truths by the end of these stories. They function as morality tales or immorality tales, they are there to warn you. They are there to say, if you don't do something about this, there will be consequences. It doesn't have a cosy ending."
You previously produced a very different series, Marion & Geoff. Are there any connections between the two?
"Marion and Geoff was quite a morality issue. It was about people's obsessions and what drives people to do things they do and that they go to extremes. Marion & Geoff dealt with that in a comedic manner and the dramatic characters in this story do the same. But I was interested in developing that idea and throwing in the idea of what it means to be heroic. What is a hero? Because potentially the things that Chiwetel Ejiofor's character has to do, takes him into a world where the risk of knowing and behaving as he does, brings terrible danger to those closest to him. Is that heroic? On the other side, there are people who cover up what they need to cover up. But in some ways they are protecting the greater good - is that heroic? So this is a much bigger template with much bigger themes than Marion & Geoff."
Was it a deliberate decision to not use too much incidental music?
"Yes. The guy who composed the music said to me, 'I'm very engaged in this. Not least, because it's difficult to see where I fit in'. An interesting score is supportive of what you don't already know. What you can't really see or hear. It has something of a sub-textual quality and I think as the journey progresses, the score comes in more as the themes start to set. But when we're setting the stall out early on, I don't need to manipulate you into feeling something, you just need to be saying, 'What is this? What is that?' If I manipulate that, it is very interventionist."
The first episode moves at quite a slow pace. Were you at all worried or conscious about capturing the audience's attention?
"The project has really grown. It started out quite small as a concept in just two rooms. When we discussed it initially, there was the backroom business and the investigation business. Then as I wrote it, the plot slowly grew. I hope the audience will feel that it is distinctive and unusual. It should be, it's on BBC Two. It's our HBO and that's really how we should be really thinking about it. If we don't do that, we will always be looking across the water. It should be a challenging show. But at the same time, it must also be gripping. We always wanted to ensure big things happen. There's a bullet in the brain, money, spiralling car chases in reverse - that's what makes it unusual. There are things happening all the time. Like I said earlier, they are mainstream in a way, but not quite what you'd expect."
The Shadow Line starts tonight at 9pm on BBC Two