Sometimes, the more serious the job, the more you laugh. Life’s too short not to have a laugh. To me, that’s part of the joy of what we do. As you view disk to disk you get to know and understand the characters and their feelings come through. What is the storyline for this new series of Shetland and how does Ruth Calder feel about returning ‘home’?

We all have a WhatsApp group together and keep in touch and I imagine there will be lots of fun messages when the show airs. However, Calder’s hostility to Shetland will challenge Tosh’s view of her adopted home and their journey into the darker recesses of Shetland's past and present will test this fragile, new partnership." What happened in episode 1? 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. The world of Shetland police HQ is as we knew it - warm, reassuring and familiar. But change is coming and with it, fresh challenges for the team. I also think Calder is a littleenviousof Tosh – sheappears to have it all, a family lifeanda career.It's hard to even describe what this journey has meant to me. I never, in a million years, thought I would still be playing this character over a decade after I was originally cast in the part. However, when Peter Ayre’s car is spotted in the hospital car park the night Ellen’s body went missing, the police head to his house, only to find a horrific scene unfolding. Peter is in the middle of a strange ritual, where he is burning a fire in the grass in the shape of the mysterious symbol from Ellen’s tattoo and chanting and singing around a bonfire, which at closer look has Ellen’s body lying in the middle of it. But if that wasn’t enough, there’s one more twist in the episode when Calder finds out her father had an affair with Ellen’s mother, Stella Quinn. Does this mean Calder has been investigating her own sister’s murder without even realising? What happens in episode 4? The crew were all wild swimming after work and I went along to Meal Beach one night and had a dip with them. I was an absolute wimp about it and took about 20 minutes to get in beyond waist height but it was so lovely. Some young people had a fire going on the beach and the water was so clear. That was really special. Inspired by Ann Cleeves' Shetland novels, Shetland is a Silverprint Pictures production for the BBC. She says:"I am absolutely thrilled to be joining Shetlandas DI Ruth Calder. It's such a hugely successful show and I am aware I have very big boots to fill since the departure of DI Perez, who was very much loved by fans of the show.

She is a wonderful mix of an absolute hoot and a consummate professional. There were days when I laughed so hard my stomach hurt and I was in danger of crying all my make-up off. But we never, ever lost focus or took our eyes off the ball. Figuring out our chemistry together was an outright pleasure and I'm really proud of what we created together. When the police discover that Rosemary's boyfriend, Liam Kenmuir, has links to Peter and his hospital pass was also used the night Ellen's body was stolen, Tosh and Calder think they've got their killer. However, it doesn't take long for them to work out that he is covering for Rosemary and she is Peter's pen friend and the mysterious sheep-killer. But did she kill Ellen?This new series of Shetland boasts a stellar guest cast – what was it like working with the likes of Phyllis Logan, Dawn Steele, Jamie Sives and Lorraine McIntosh? And then there’s the weather! One minute we had this horizontal rain and the next, a heatwave and it was like the tropics and everyone was going wild swimming. I felt like I was on my holidays. We have both grown older, we are both mothers, we both have a huge amount of experience under our belts. It's nice to be able to chart that journey for myself both on and off camera but this series, to be standing in front of the board, taking charge of the team...I felt like I had grown wings. 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.