Tonight sees the return of Channel 5 cop series Suspects. Starring Fay Ripley, Damien Molony and Clare-Hope Ashitey, the broadcaster's first original drama in eight years focuses on the procedural - but not in a manner us TV viewers are accustomed to. The entire script is improvised. Now, we know what you're thinking but, take it from us, this works. The first series found itself up against BBC2's terrific Line of Duty and, frankly, didn't get the attention it deserved. 

Now Ripley's DI Martha Bellamy is back, flanked by DS Jack Weston (Molony) and DC Charlie Steele (Ashitey). We spent a day on the set of Suspects to see what all of the fuss was about...

How do you go about filming a show like Suspects? 

Fay Ripley: It’s only improvised on a level. There's no script but there are strict guidelines. You can’t really freefall off the point because they’ll only cut it. We’ve got good at knowing what they want us to do so there's a bit of a knack to it. We’re not making it up as we go along. We’re not suddenly in mid interview deciding that actually they didn’t use a gun, they smothered them with a pillow. 

So, filming must be pretty full on?

Damien Molony: It’s been two and a half weeks of pulling your hair out, feeling shattered and trying to remember suspects’ names. It’s brilliant fun and when we finish in a week’s time, we’ll miss it. 

Clare-Hope Ashitey: You can’t be totally prepared. If you are, it loses something. It’s kind of terrifying but you realise that’s the magic. 

It must have required a giant leap of faith when you first signed up to Suspects? 

FR: As much as I’m scared of doing something different, I’m much more attracted to doing something new than I am to doing the same old s**t. Things have attracted me in my career and life where there’s a risk involved. I write cookbooks – many people have told me not to do that as well. I don’t know about the others but you weigh these things up and think this could be a massive mistake or really good. 

Have you picked up loads of impressive police facts? 

DM: We have a police advisor called Steve. I just did a scene before lunch and I came in and thought I’d absolutely smashed it. He was sitting right there and looked at me and said ,"You never leave a prisoner on their own. If he runs off that’s seven days pay for a police officer."

C-HA: I left a prisoner as well before lunch! They didn’t say cut so I didn’t know what to do.

Will we be seeing more of your characters' private lives? 

FR: We are investigating a crime and the people who committed it are all the emotions you want to think of – scared, jealous, angry, hurt, panicked. That’s what you’re required to do as a criminal but as a policeman, you’re not allowed to be emotional, scared or panicked. It would be weird. There are policeman who are allowed to do that but those are in other shows where you get to see their inner world. You will never, ever go home with us. Every other cop show you’ll get in the car and go home and see them cry at the end of their bed when they’ve had an awful day. You’ll see them have an affair and divorce their husband but you’ll see none of that in this show because that’s not the point of it. 

Suspects returns to Channel 5 tonight at 10:00pm