"I've never done a job this intense. I was in every day and pretty much every scene, so it was exhausting," she revealed. "Your day starts at five and doesn't finish till 10. But I loved it."
Siobhan plays DI Liz Nyles, who works in the witness protection department, shielding those who've given evidence against criminals and are then hidden in safe houses.
But she realises one of her team could be leaking information when there's a murder at one of the hideouts and as DCI Hannah Wheatley (Katherine Kelly) arrives to look into possible corruption of the unit, Liz starts her own investigation.
image [https://cdn.magzter.com/1583517504/1742004687/articles/bn2I86mHecMcykXdYKsys/2072022720.jpg]
She focuses on her younger, married colleague DS Paul Brandice (Barry Ward), who she has been having a secret affair with.
"She's a woman in her fifties with a 16-year-old daughter and she's just become a full-time carer to her dad," Siobhan explained.
"Like hundreds of thousands of women, Liz is trying to keep a balance between personal and professional, so hopefully her character will resonate with loads of people - until that all gets blown up, of course.
"DS Paul is a new officer in the protection unit. He's fun and makes a play for her and she falls for it. It's a bit of fun for both sides, even though she knows it's morally wrong- then feelings come into play. Like a lot of people, she's probably quite lonely, going home to a teen and an elderly parent, so she did this just for her as a bit of an...