Face to face in her exclusive interview with The Scotsman, Ashley Jensen is telling me about her bid to spot a real life killer when she was filming for the new series of BBC crime drama Shetland, which hits the screens this week. How in between takes the crew would scan the horizon for signs of the orcas, or killer whales, which are often spotted in the sea around the islands.

“But no, I didn’t see any orcas! Not for want of trying!,” she says. “Every day you look out hoping to see one, and some of the crew had an orca app - but I wasn’t lucky. It was the same with the puffins. I saw a puffin corpse with Alison [O’Donnell, who plays ‘Tosh’] and we only knew this skeleton was a puffin because of the beak, and I was like ‘seriously, is that all I’m going to see?’”

Jensen was hoping to catch sight of the island wildlife when she joined the cast for the eighth series of the hit murder mystery drama set on Scotland’s northern archipelago, after the departure of Douglas Henshall as lead, but while the odds are she and the team get to the bottom of whodunnit in the latest crime wave to wash across the islands, spotting orcas and live puffins remains on her to do list.

Surely it wasn’t that hard to spot some puffins, they’re all over the place - even the hardened criminals in the new series carry books about them in their pockets.

“I know! But I would work and go home at night and prepare myself for the next day. You know it’s my first time in the job and I thought ‘I can’t be arseing about and going looking for puffins all night when I’m up at six.’ But a lot of the crew would go off and come in with photographs and films of puffins, with their funny little noises, thousands of puffins, and I’d be like ‘the puffins, the puffins, I need to go and see the puffins…’

“Then on the last night, I said to my driver ‘come on, we’ve got to go and look for these bloody puffins, we’re leaving tomorrow’, but it was too late at night and they’d basically all bloody gone to bed and were all in their little burrows.

“We did see two or three renegade ones going ‘rwaaak’, ‘rwaaak’, [she makes a sound that’s a cross between a squeak, a grunt and a chainsaw] and that was it. It was ‘quick, get a photograph of them!’”

While this is Jensen’s first visit to Shetland, it’s a welcome return to her homeland after last year’s BBC drama Mayflies, alongside Tony Curran and Martin Compston, for which she has been shortlisted for a BAFTA. Meanwhile, for the character she plays in the series, DI Ruth Calder, it’s a somewhat more reluctant homecoming as the Shetland native who left for London at 18 is only back because a case has dragged her there.

“She left as soon as she could,” says Jensen, “and we find out the reasons as the show progresses. She’s not faced a lot of what she ran away from and is pulled back against her will, not because she doesn’t like Shetland, but because it causes her to face her past and relationships with people who knew her.”

For Jensen joining Shetland was a no-brainer after a career that has spanned three decades and stage, screen and film. Brought up in Annan in Dumfries and Galloway, she studied drama at Queen Margaret University College in Edinburgh then landed a role in the 1993 BBC drama Down Among the Big Boys playing the daughter of Billy Connolly’s criminal Jo-Jo Donnelly before gaining fame in the US on Ugly Betty (2006-9) and starring alongside Ricky Gervais in Extras (2005–2007) for which she was nominated for an Emmy and then alongside Mark Bonnar, Rob Delaney and Sharon Horgan in their Channel 4 comedy drama Catastrophe (2015-19). She played a DI in Robert Carlyle’s debut film The Legend of Barney Thomson (2015), and more recently super sleuth Agatha Raisin for Sky as well as teaming up with Gervais once more in After Life.

As well as Jensen, who joins series regulars including Alison O’Donnell as Tosh, Steven Robertson as DC Sandy Wilson and Lewis Howden (Sgt Billy McCabe), there is a whole host of new characters in the new series, including Phyllis Logan (Guilt, Downton Abbey), Jamie Sives (Guilt, Annika) and Dawn Steele (Holby City, Granite Harbour).

So how did Jensen approach joining such a long-established show with a huge fan base and much-loved main character in Jimmy Perez, played for so long by Henshall?

“It’s big boots to fill,” she says, “and if I’d gone down the route of thinking about that too much, it could have been quite crippling.

“I had to look on this as a new six-part series with nothing that had gone before and nothing after. I absolutely loved it. I loved the experience of being able to go and film on Shetland, a place that I never in my wildest dreams ever thought I would go. It’s like nowhere I’ve ever been before.”

“It felt magical, the whole ambience of the place, both bleak and beautiful, silent and noisy, large and small. With orcas, seals, puffins and Shetland ponies, it almost feels magical and mythical. Often it’s not until you go away, for me from Scotland, do you appreciate what you had. When I did Mayflies last year and Shetland this year I just really felt like I’d kind of come home.”

Did Jensen identify with Ruth Calder as the new addition and did her approach differ to that of the Metropolitan cop who knocks back the welcoming offer of a scone by stating her desire to just get on with the job?

“No. Ruth’s much more forthright and cares less about other people’s opinions, although when you get to a certain age you care slightly less about what other people think about you. But I think I’m a bit more accommodating than Ruth Calder. She was literally just there to do the job, but Ashley’s there not only to do the job but also to have quite a nice time. For me life’s too short to be having a miserable time or stressing about ego. I just want to get on with everyone and for everybody else to have a nice time as well.

“So I think Ruth’s more direct, throws her weight around more, whereas I would definitely have accepted the scone.”

When she was presented with the Shetland script Jensen didn’t have to think twice.

“It really was a page turner, and the colour, dialogue, nuance and well-rounded characters made it a gift. Ultimately everything comes down to the script, and the story was so engaging.

“And I felt that Ruth’s not black and white. She could sometimes be unlikeable and rude, formidable, but she’s very good at her job. To be poetic about it, she’s a little bit like an island herself, she’s built this barricade and nobody’s going to get in. She is quite isolated like the island of Shetland.

“She has to be there for her work and get on with it, but ghosts and demons from the past are going to unfold.”

While Jensen is Henshall’s replacement as lead, in conversation she emphasises the ensemble nature of the cast and how DI Calder is working in tandem with Tosh, played by Alison O’Donnell.

“People ask what are they like with each other, are they ‘hmmm I don’t trust you because you’re a woman’ or ‘we’re two best friends fighting against the world’? It was neither. Tosh is very entrenched in the islands and very good at her job there, whereas Calder’s coming from The Met, from gangland crime and murder and built up areas, so it’s almost like urban policing versus rural policing, and they’re coming together.

“Calder could have been a man to be honest, it didn’t matter that she was a woman, in the beginning. But there is a respect there. Calder begins to see that Tosh does know what’s she doing, but is undermining herself by calling herself, ‘Temporary DI’ and is saying, ‘just stand up and be counted’. I thought that was nice. Introducing a new character also shines a light on Tosh.”

While Dougie Henshall became synonymous with his pea coat, was there a similar desire for DI Calder to have a signature look, just as Tosh has her waterproofs and Sandy his leather jacket?

“The iconic donkey jacket, yes. I think it’s important for a TV detective to have a silhouette so you can almost see them coming over the horizon, like Vera has her hat and coat, Agatha Raisin had the sharp bob, lips, nails, high heels and handbag. Obviously Shetland is not comedy and we have to accommodate the weather, and also I feel the cold, so we arrived at the city cashmere coat, slightly out of place. Cashmere is warm, but not hugely practical when it’s wet and the wind is blowing… And then we ended up filming during a heatwave in Shetland and I was dressed head to toe in cashmere…” she laughs.

“We even went on a little journey with the hair, in that it started off very straight because Ruth hadn’t brought her straighteners as she didn’t expect to be there long then the weather got in the way and it becomes more unkempt and unruly as the series goes on.”

Did Douglas Hensall give her any tips about being in the show, or about the islands?

“No, I don’t know Douglas Henshall. I’ve worked with him many, many moons ago in Down Among the Big Boys by Peter McDougall and Billy Connolly was a criminal and I was his slightly spoiled daughter and was going out with this guy played by Dougie Henshall, who was a police sergeant on the case of my father. So I walked down the aisle and was about to marry him, but our paths haven’t crossed since then really.”

However, the regulars were able to point Jensen in the right direction for top pit stops and places to walk her two golden retrievers.

“Yeah, I did get all of that. Alison told me about the places to eat and the beaches to go to because my family came up and the dogs were running about, so I know lots of little places now. I found a very good junk shop - I’m partial to an old junk shop - and Frankie’s fish and chips shop [in Brae] which is the most Northern fish and chips shop in the British Isles, and there were lovely little restaurants and she told us where to get a nice coffee and nice meals and stuff.

“But we were both quite anti-social when we were doing the job, because she had her wee kids with her and I was going ‘I’ve got to learn my lines, I’ve got to know what I’m doing for tomorrow!’ We had a great time together. She’s one of these people I feel as if I’ve never not known; we got on like a house on fire and giggled and laughed and bounced off each other.”

It might be Jensen’s first case in Shetland, but she has previous of playing a sleuth, in the form of Agatha Raisin, the kitschy fun comedy-drama based on [Hamish Macbeth writer] M C Beaton's books, which has been running since 2014 on Sky.

“I was very relieved I don’t have to scale any walls in four-inch stilettos like Agatha Raisin, although I did quite enjoy the challenge of doing my own stunts on that because I love physical comedy. I don’t think there’s enough of it in the world.

“I absolutely adored playing the part. I think it’s allowed me to bridge that gap of comedy and drama, because that was whimsical and camp and silly and heightened and physical, whereas Shetland is brooding and intense and harrowing and visceral. They’re poles apart. We’ve got the same face and the same accent but more than that there isn’t much similar. I feel very lucky that I’m able to play both parts.”

Between the comedy of Agatha Raisin and the brooding intensity of Shetland comes After Life with Ricky Gervais, her Extra’s co-star, in which she played nurse Emma to his grieving widow in three seasons from 1919 to 2022.

“I think After Life also helped me bridge that gap, because I jumped from that into Mayflies and there weren’t many laughs in that. Although it is funny… maybe it’s me coming from comedy, I don’t know, but I think even in the most stressful, harrowing situations, there is humour to be found.

“I’ve found myself in situations and I’ve ended up cracking a wee comedy line and people kind of going ‘oh that’s dark’ or ‘yeah, aye, right enough’ and I think that’s part of life. Having been predominantly known for comedy I do quite like to get a wee element of it in even if it’s just a look or a wee line to something that might not have been funny on the page. I’m all for adding layers and finding something else, even just being physical and taking my coat and scarf off when I’m doing it.

Jensen is used to taking it all in her stride after a long career in which she’s worked with big names like Carrie Fisher, David Bowie, Samuel L Jackson and Billy Connolly. Did those starry people make an impression or give her advice that’s stuck, or has anyone else ever said anything she’s always carried with her?

“Well my granny used to say ‘what’s for ye will no go by ye’ and I carried that around with me for a while but then I thought ‘well, I agree with that to an extent, but you’ve got to put in a wee bit of effort yourself’.

“I wish I could say David Bowie gave me a pearl of wisdom. I remember I went up to him and asked him for his autograph and he said ‘this is for your mum, isn’t it?’ and it kind of was for my mum and he was like ‘oh, I knew it, I knew it’.

“The one that got away was Carrie Fisher on Catastrophe. We’d worked with her in the morning and she was such a raconteur and me and Mark Bonnar were sitting there just listening to her talking tales of her life and Star Wars and her mum [Debbie Reynolds], and I’m never one for going ‘can I get a selfie with you’, because I don’t do Instagram and social media and have managed to avoid all that, and then I went ‘och, do you know what, it’s Carrie Fisher!’ I thought ‘I’ll let her have her lunch then ask when we get back, but she had her lunch then left immediately and I didn’t get a wee selfie with her. I was wanting to get a photograph of Princess Leia for my son… well I was saying it was for my son…”

So did her mum ever get the Bowie autograph?

“She did. She was delighted.”

With one series of Shetland about to air does Jensen think there will be more to come?

“I have absolutely no idea. But I would do it again in a heartbeat, not only to explore where Ruth Calder’s journey takes her, but to go and see the bloody puffins.”

Shetland, BBC One & BBC iplayer from Wednesday 1 November, 9pm.

Ashley Jensen: When I did Shetland I just really felt like I’d kind of come home