Where do we find Robin at the beginning of this series?

Robin has put an offer in and is buying her own flat for the first time. She's never lived alone. There's been this whole period of growing up that she's not quite had since she's been with Matthew.

There's a real sense in her that she's found independence, this confidence and security in her freedom. I feel like she's in a good place.

Strike goes in for a kiss early in episode one. From your point of view, what do you think is going through Robin's mind?

Oh, I think it's just everything. There have been times when it's what Robin would have dreamed of. But actually, she genuinely in the moment doesn't trust that he will… Once you cross that line, it's done.

How do you undo that as business partners?

You can't. If you go to the other side of that kiss, it is the complete unknown. I think there's a real fear in Robin, an insecurity about how he feels about her. Because she just doesn't believe that he won't regret it. I think she just can't stand the idea of there being any regret on his part about it.

I think Strike would have to profess his undying love for her before she would feel comfortable with him crossing that line.

He's the person in her life that means the most, so it's very delicate. There's a lot going on in that split second. The split second for Robin is just “No, don't want to go there. Can't go there.” And then immediately it's “Oh, what if he meant it? What if that could have been the start of something?”

Robin has many disguises, and this season is no exception. Why do you think Robin's so good at doing that?

I think she initially felt quite comfortable doing accents and the more that she does it, the more she feels comfortable doing it, the more she gets away with it, it's like Venetia Hall has now become a fixture.

Do you think in some ways the disguises are helping her deal with her past traumas and the disguises allow her to be free to be whoever she wants to be in that moment?

Oh yeah, with Jessica, one of her personas in this, she would allow Jessica to ask questions or make decisions that Robin never would. Which is why they're useful. They’re alter egos.

Robin has a tough verbal and physical confrontation with Charlotte’s partner, Jago Ross. Can you tell us why this is significant in giving us more insight into her character?

They’re investigating Jago Ross because he’s Charlotte’s partner and, to get Strike out of a sticky situation with those two, Robin doesn’t want to allow his mistakes to ruin her business.

But while investigating Jago she realises what a horrible, misogynistic piece of work he is. He is an horrendous child and woman abuser. Physically and emotionally. So, when she's face to face with seeing it, her whole history comes out.

He symbolises everything that Robin hates. Misogyny and also the class arrogance that he has. As a father and leader of the household, he's in such a position of power over these young girls that he should be loving and creating a nurturing environment for them, and he's not.

So he's, in Robin's eyes, so undeserving of every privilege he has.

The Land Rover's back! Why does she hang on to this car? Why does she love it so much?

God knows, if I was Robin I wouldn't go and stake out in that Landy. But we all love the Landy. I think because it's Robin's family car, and I think that what I love about Robin is that she's not frivolous at all.

If it works… She's not going to buy herself a new car unless this one breaks down. Maybe there is a sentimentality with it as well, but it's a fully functioning car.

It's weird how cars and things like that can become characters in a way. I know that’s the case when I watch particularly detective shows… we all wanted like Saga Norén's Porsche 911 that she drove in The Bridge.

I think there's a history between detectives and their cars. Without a doubt. And so, you know, it's Robin in the Landy!

What do you think about the gaming online?

The whole premise of the mystery in this series is based on the anonymity - online trolling and online bullying. Anonymity gives you a power and a confidence to do and say things that you would never say to someone's face.

There are fine lines in this between insecure people bullying because they can, and evil people with a genuine, dark motive. How do you figure that out? Is this just a bullied school kid in their bedroom taking it all out online? Or is this an organised extremist group, with wider political motives? You often can't tell online because of anonymity. And I think that's what this series is about.

How dangerous do you think that is generally - the fact that there are these two worlds? What's your view of anonymity?

I don't have a firsthand experience with it, but I think, when there is anonymity and false confidences, people can be very easily manipulated.

We tackle how dangerous online abuse can be and how dangerous it is that people can manipulate and twist people's vulnerabilities online. I think that's quite dangerous.