The star of the psychological police drama reveals five secrets from the set

1 The series is set entirely around the interrogation of suspects and my character, DCI Natalie Hobbs [pictured], is neurotic and lives for her job. Even her hair is precision perfect. I was offered a wig but I hate faking it so for the month we were shooting I had regular cuts and dyes to keep her bob perfectly straight and black.

2 We split the day’s filming between the interview room and observation room so we don’t get cabin fever. The interview room is completely soundproofed and the observation room, where police watch the suspects and interviews through a two-way mirror, has a different vibe – you feel you can relax a bit.

3 There’s no action, it’s pure dialogue and that means there are lots of lines to learn. It feels special arriving on set knowing you have it all in your head and you can then be completely adaptable if there are changes, particularly as we have no rehearsals.

4 It’s only our second series but we’ve attracted top actors to play our suspects. Kit Harington [inset] from Game Of Thrones started with a great seven-minute monologue, which he nailed first time. Sophie Okonedo brought gravitas, while Sharon Horgan made it all seem easy.

5 The episode Kit’s in is about date rape and Sharon’s is about a vigilante, and they led to a lot of discussion on set. The series challenges you as a viewer; you start with preconceived ideas about the characters and think you’re on safe ground, then your view shifts as the interviews proceed. They’re complicated, nuanced stories – life is like that.

Available now, Netflix