The first series of Primeval ended with the shock revelation that Stephen Hart had slept with Professor Nick Cutter's wife Helen. As series two of Primeval has progressed, Stephen Hart's faith in Cutter has started to diminish – a character development that James Murray is pleased to see in the ITV adventure series…Words: Paul Simpson

Is Stephen feeling alienated from the team this season?

They're subtly separating him. It's a great device. He becomes increasingly disillusioned with Cutter's theories and whether what they're doing is right or not. And him sleeping with Helen way back when doesn't help much.

Were you aware of that when you started series one?

I don't think that particular strand of storyline was set in ink yet. I think the writers adopt an approach that the first and foremost driving theme of the whole story is the anomalies, the dinosaurs and the creatures, and I think they wait till the last minute to decide what to do with the characters, which can have positive and negative outcomes.

Originally we set out with two characters, Cutter and Stephen, who are best buddies, but they're in essence similar beings, albeit he's a professor and slightly older. They're jostling for the same kind of space. Adrian took it away from the buddy thing and thought, "How are these guys going to co-exist with similar wants in life?"

What's his relationship like with Helen this series?

She is very much more front-footed with him in this series. The way I approached it was that the cat's out of the bag. These two know each other more than we first let on. Many moons ago, it was all very physical, as you can imagine between a lecturer and a student.

Now it seems obvious that she's trying to manipulate Stephen. She needs him for something, and she's doing it the only way she knows how, trying to press his buttons. He's all too aware of this, and knows that she's trying to play him. But in the same breath, she's saying things that he wants to hear, that he agrees with now, which are counter to Cutter's theories. He's torn. When you add a little bit of her inherent seduction into the mix, it hopefully ups the stakes a little bit.

Did you have a chance to sit down with Adrian to discuss Stephen's future between series?

There were some calls back and forth during the development of the scripts of series two. Adrian is very amenable and will listen to suggestions. The problem is with so much going on in these episodes, to get a small percentage of where you suggest your character should be going, you're lucky. It's all about trust and faith, and you have to have a lot of faith in writers.

Do you think the death of the sabre-tooth's owner Valerie in episode three pushed Stephen over the edge?

It did. That's what Adrian and I discussed. If you become increasingly at odds with what and who you're working for, and then something huge happens, like the death of somebody, it compounds your doubts and gives you a justified platform to voice your doubts. All these are well placed devices for the rift to become wider and wider until something's got to give.

Do you think there is consciously a tougher attitude to life in this series?

I think they've stepped it up. It's a tough balancing act. You've got an ITV primetime show on a Saturday night so you've got to appease that side of things, and at the same time you've got a fantastically ambitious concept which can only benefit by being enriched by more realism. I think they've tried to introduce a little bit more realism and a little bit more shock. I don't know whether it's worked or not, but I think it was a good idea.

Primeval goes one way then another. Just when you think you're comfortable with it being a well made, reasonably light-hearted, entertaining family show, it throws something into the mix that makes you sit up a bit.

The way to keep audiences wanting more is by getting them to invest in the characters. You can spend millions on a show and have the most wonderful effects but if you don't care about the people, who cares? I think episode four really did introduce that. It can only snowball from there. You can't show a little bit of emotion between characters then take it away – it's got to go somewhere.

Were you surprised that Stephen got things so wrong in episode four?

I wasn't surprised, and I thought it could only serve to make him a more interesting person. I thought that they were trying to ostracize Stephen more, and if they got him to make a mistake then it would confuse him, and add to the confusion as to whether he's right or wrong. Had he got it right, it might have given him more of a voice against Cutter. But I think Cutter is handling it incredibly well and could have kicked him into touch a long time ago considering what Stephen did. But he knows Stephen's useful, and they did have a very close relationship, which is straining to be rediscovered.

Having fallible characters is a good thing. I pleaded with the writers to give Stephen something that isn't just about winning the day. It becomes awfully boring to play after a while, and awfully boring to watch in a show where everybody else is doing the same.

Were you aware that this season was going to be as big as it is?

We didn't know they were going to step it up as much as they have. Normally as an actor, if something gets recommissioned, it's because the execs want more of the same, and the word "more" is the one that's underlined and highlighted with a big pink highlighter. This show has got to constantly progress, or go another way. Although it's a great concept, the worst thing you can do is get lazy with it.

Is there another big shock at the end of this series?

The end of this series is mammoth compared to the end of the first series in every aspect: character, monster, action. Episodes six and seven are in essence one story told over two episodes. They have different creatures in both episodes, but it's the same story. That will hopefully be a real bombshell to end it on.

Towards the end of this series, everybody shows their true colours, and it really should be something good to watch!