Ashley Jensen has the unenviable task of taking over from Douglas Henshall in season eight of Shetland.

So who better to tell us about her character than Jensen herself?

Tell us about your character, DI Ruth Calder.

“She’s formidable, she’s strong, she’s a woman in a man’s world. Ruth Calder’s built this little barricade around herself – she’s almost like an island herself.

However, she’s very much an urban detective and is resentfully drawn back to Shetland. This case makes her confront herself, her past and the things that pulled her away from her home in the first place. Her resentment all stems from her history with the Shetland Isles and why she left all those years ago. It’s not that she doesn’t want to be there, the issue is she’ll need to face the past she left behind.

Ruth doesn’t expect to be in Shetland for very long – she comes with a tiny wee case and she hasn’t packed her hair straighteners.”

What do you think are Calder strengths and weaknesses?

“She’s very direct, she’s quite formidable with years of experience so she’s incredibly focused and very driven. When it comes to this particular case, however, her weakness is that she lets her personal issues get in the way a little bit.

I think if she took herself aside – and worked more as part of the team in the beginning – she’d achieve more. At the start, there might be a slight air of superiority about Calder with her taking the view that the Shetland team don’t work quite as well as her London team do. But she begins to realise that there are strengths in not jumping in with both feet at the same time. This is as much a personal story as a professional one for Calder.”

What is the storyline for this new series of Shetland and how does Ruth feel about returning ‘home’?

“Ruth Calder is called to a London crime scene for a murder that could be connected to gangland crime. The case inadvertently takes Ruth back to the Shetland Isles because the eye witness, Ellen Quinn [Maisie Norma Seaton] is suspected of going on the run there, back to where she’s from. Calder feels an affinity with Ellen – after all she’s a girl who ran away from her life in Shetland and started a new one in the big city.

Ruth is used to getting things right and this is a complex case which is layered and doesn’t quite go the way she expects it to. There are so many different paths that she ends up going down.”

How does Calder feel about Tosh and policing in Shetland?

“Ruth is used to ganglands and murders, race crime and knife attacks…big urban crimes. So when she comes up to Shetland her heart sinks as she’s suddenly back in the world she left behind.

I think the pace of Shetland is an issue for Calder because it’s much slower than London and the urban policing she’s used to. Ruth’s a little bit of a lone wolf, she often dances to her own beat.

Tosh [Alison O’Donnell] is just as professional as Calder but needs to find her own way to navigate a new working relationship – ultimately they respect one another. They don’t treat each other with caution, I think that it’s just literally two different approaches to police work coming together but there is an element of good cop, bad cop.

So it’s not Tosh that Calder has an issue with – it’s the two different approaches to work. Both are valid and, as they start to work together as a team, they see their strength together.

If anything, Sandy irks her more because they probably knew each other in the past – that’s the back story Steven [Robertson] and I created anyway! I always think drama is drama when it’s about people’s relationships with one another.”

How do Ruth and Tosh get on when they first meet and how do you see their relationship progressing?

“At times, Calder almost acts like a big sister to Tosh but that might come across as nipping at her. There’s a glimmer of respect there that builds and builds – but that’s not to say that there won’t be moments when they annoy each other!

I also think Calder is a little envious of Tosh – she appears to have it all, a family life and a career.

There’s absolutely scope for them to get on and work together, they just need to get into each other’s groove. There will, of course, be moments of conflict which is always great because if everybody gets on all the time, it’s a wee bit boring.”

What was it like joining an established cast like Shetland?

“Everyone from the cast and crew were very welcoming from the start and genuinely excited to be back, as much as I was delighted to be there, playing this wonderful complex, complicated and yet confident character. Alison and I got on immediately and I hope that chemistry translates on screen.

The introduction of Ruth Calder creates a different energy for the original cast members and so we see new and different aspects of their characters, as we get to know DI Calder herself. ” 

How did you find the Shetland experience?

“I loved it actually but to be honest as soon as I read the first scripts I was like “I’m in!”. The writer [Paul Logue] has given everybody a rounded character even down to the hitmen, Howell [Don Gilét] and Nowak [Arnas Fedaravičius]. Just the nuance and the detail of every character is amazing.”

What can viewers expect from this new series of Shetland?

“I feel you can watch this new series of Shetland never having watched any of the others – you don’t need to know the back story. Bringing in a new character like Ruth Calder, it shines a light on the established characters like Tosh and Sandy which the fans of Shetland know and love. I think that when something has been around as long as Shetland has, there’s a familiarity about it but this time around, we’re looking at the same show from a different angle.”

Shetland (series 8): Wednesday 1st November, 9pm, BBC One