There were three main Twitter reactions to the opening episode of Poldark last Sunday.

There were some people who hated it. There were some people who loved it and also thought Cornwall looked quite nice. And then there were most people - most people of the female gender anyway - who just went, "Aidan Turner. Phwooarr".

Heida Reed now has to live with the fact that she is the woman who turns Aidan down. Well, not her exactly. Her character, Elizabeth. The woman who promised to be true to Aidan, or rather Ross ("look, he's taken his shirt off again") Poldark and then as soon as she thinks he's dead (as if that's an excuse) turns around and gets ready to marry cousin Francis, only for Poldark to turn up in time for the wedding. Awkward.

Those late 18th-century girls with their corsets and willingness to conform to societal conventions. What were they like? "I think there are so many people in the same situation today," Reed tells me over tea and water near London's Covent Garden, "where circumstances have made them go with one person and then another person comes back.

"If I was in that situation it would just be as hard. It doesn't mean because I have more freedoms as a woman that I would go: 'oh you're back. I'll leave the person I genuinely love and have promised to marry.' In that respect I don't think anything has changed really."

In short, there's nothing new romantically under the sun. Well, apart from Tinder.

No, if it's change you want, maybe you'll have to look at the trajectory of Heida Reed's career. Because here she is all corseted up on a prime-time Sunday night telly drama. Something of a step up from the odd part in Silent Witness and DCI Banks. It seems like things are taking off for the actress.

"I'm not going to lie. That is how I feel," she admits. "But I don't like feeling that way in case nothing changes. I definitely haven't put all my eggs in one basket in order to protect myself. I've been in TV series before where I had much higher hopes for them and they didn't really go anywhere. And I'm grateful for that now because it means that if and when I'm in something that might actually change my career I've already been grounded by disappointment."

So there you go. Heida Reed is more a glass half full kind of girl. Other things I can tell you about her. She's 26; she has never watched the original 1970s BBC version of Poldark. ("I don't think that would be helpful."). She'd like to work with Wes Anderson. She's eaten not just one deep fried Mars bar in her time, but two. ("It was one too many. You only need it once in your life.") She loves board games and travelling and, oh yes, I forgot to mention. She's really Icelandic. Don't let that posh accent fool you.

She's not even really a Reed if truth be told. Her real name is Heida Run Sigurdardottir. Ask her how it's pronounced and she sing-says it in a lovely, trilling Icelandic voice that sounds like water falling over rocks. (Heida, by the way, should be pronounced Hay-da not High-da. That's the kind of information you'll need in case you happen to be in the same room with her at any point in the near future and you want to ask about Aidan's naked swimming scene in episode two).

When she came to London at the age of 20 Hay-da still had a strong Icelandic accent. But she's worked on that. "It was a realisation in drama school that I didn't want to be in a bracket on my own. I wanted to go up against the best girls in my year, the talented girls who were getting all the good parts. I felt I could do that but I had to convince everyone that I can. I had a very good speech coach and instead of changing my accent when performing I just decided to do it overall. And then I was advised to change my name. Nobody can pronounce my last name anyway."

Does she still think in Icelandic? "It completely depends on what's going on in my head. I think I mostly think in English. There's a very strange thing that happens sometimes - this might be a bit dramatic - but if I really need to go deeper within myself it's sometimes nice for me to switch into an Icelandic train of thought. It brings out something different."

Are they different mindsets? "I think I'm slightly more naive in Icelandic. I relate back to my teenage self. I left Iceland when I was 18 so I grew up in the world. So whenever I go back to Iceland I do always feel much younger. I always go back to my parents and sometimes turn into a teenager: 'mum, when's dinner?'"

Reed was raised, the middle child of three, in a suburb of Reykjavik in the house her parents still live in. Dad is a pianist and music teacher, mum a dental hygienist. Her daughter has, as you might expect, lovely teeth.

What are the most ridiculous preconceptions people here have about Icelanders, Heida? "Most of the things that people think are true. We are very strange. We do believe in elves, or what we call 'hidden people'. We do have 13 Santa figures."

Did she grow up eating puffins and sheep heads? "Puffins, no. Because, first of all, they're very expensive. Tiny little meat. And I feel it's barbaric for such a small amount of food. Also, they live only in the west so they're not as easy to come by. Sheep heads? I grew up with that! I wasn't happy when it was for dinner but it was for dinner."

She's been here six years now. What is it about the British that makes her scratch her head? "There's a weird thing with British people. They hoard a lot. I do think it's quite endearing. British people in general I find quite endearing. It's a different way of living and it's very much comfort over style.

"You're obsessed with central heating and not turning it on. And that drives me crazy. I come from a place where the houses are heated geothermally and there's always this lovely, natural warm heat. Here I have this whole war with whoever I'm living with during winter."

She's on a roll now. "The whole tea thing is absolutely spot on. When British people go 'you think we just drink tea and eat biscuits.' It's what you do! And I've really noticed people get really excited about tea. I find that the funniest. I feel I'm very much in an English home if I wake up and the first thing they do is offer me PG Tips and a bacon sandwich."

Reed always wanted to be an actress. "My dad said to me: 'you should become an actress because in that way you can get an outlet for acting like an idiot all the time, running around and singing.' And I thought:'that's the best idea I've ever heard'."

As a teenager she signed up with an Icelandic casting agency that sent her to India to go up for commercials. "Basically modelling." The plan was to go there and then come back after three months. But she fell in love with the place and stayed for 18 months. Didn't even go back to finish school.

"It's the colour and the chaos of it all," she says, trying to pin down that love in the yellow filmy light of the place and in its scents and odours. "There's this pungent smell of garbage here and there, but then you might be somewhere else and there will be lovely smells of incense and spices. And the people are genuine and open-hearted. It's just such a different world."

She went travelling for a while and then came to London to go to drama school. Why not Iceland? "I wanted to be a small fish in a big pond," she says.

Thus started her reinvention. "I think my strategy was to come here and throw people off the scent a bit. Only because I'm just playing the game, because I want to go up for all the things, not just be put in a bracket."

There's a fair amount of ambition at play here by the sounds of it. And a fair share of commitment. She's put in the hard yards required of young actors. Played small parts, did the Edinburgh thing. "I went for the Fringe a few years ago. We did the most depressing play on Earth. Cross Purpose by Albert Camus. Basically about how God is dead and there is no purpose in life. Wonderful to do for 30 days straight in a tiny, little venue with maybe five to 10 people watching every day. Three of us sharing a bed for a month and it was kind of awful and we argued so much. But in hindsight all I remember is how beautiful Edinburgh was."

As already established, she did sample the deep fried Mars bars. Irn Bru? "A taste of it. Horrifying. Horrrrrrrrifying! Surely that's not good for you?"

Her first acting job was a role in the adaptation of David Nicholls's novel One Day. "It was a very small part but it was my first job ever. Big film. Anne Hathaway. Jim Sturgess. I played one of his many girlfriends in the film and it was a great experience."

Or it was until she watched the film and realised she'd hit the cutting room floor. "I am in it for a second I guess, but I had two great little scenes. Unfortunately they didn't make it in the final edit."

Then there was that aforementioned TV series. Jo. A cop show starring no less than Jean Reno. You don't remember it? That's the problem.

"There was a lot of money in it. We were taken care of immensely well and we shot all around Paris. There were high hopes for where it would go. And then, as so often when it comes out, it's just a different kind of animal to what you thought it would be."

At least it got broadcast. But not enough people watched it. "We were all hoping that we'd go back for a second series but that didn't happen. And we were all quite sad about that ... mostly because it was Paris. I had this plan. I was going to go and study French and then go back for the second series and talk French all the time."

It's not a great start to a career, is it? In your first two big jobs you end up on the cutting room floor and then you don't get recommissioned. But Reed can see an upside. "Those are the two things that everyone worries about and it's already happened to me. I think my feet are very grounded when it comes to the industry."

Like we said, half glass full.

If anything her glass must be close to the brim now she has Poldark on her CV. Making the costume drama meant long days, early starts and corsets. "I had the most hair which means my pick-up call is the earliest. Five am. And then being reined into your corset. Many days you were just not up for it. It completely changes you being in that. And you were sometimes in it for about 10 hours and your ribs are completely reined in."

But it does look lovely, she admits, and if nothing else, "it was almost worth putting it on to have it taken off at the end of the day. There's an almost euphoric experience when your ribs would expand and the air would come back in. The sense of freedom."

So basically wearing corsets are a form of exquisite torture. A bit like love then. When was the first time you had your heart broken, Heida? "I was 17 and it was my first love and in my head it was a Romeo and Juliet type of love. He was a very bad boy. And I was a very good girl. But we connected. I thought we were soul mates. He broke my heart absolutely into little pieces."

The swine. "No, I thank him today because I am a big believer in getting your heart broken as many times as you can because it reminds you that you're alive and it ignites all those little things that sometimes dwell too still in you. It's horrific but once you're out of it I feel it's a kind of rebirth. A regeneration of energy."

Does that mean you'd manipulate a situation just to have your heart broken, Heida? She looks at me like I'm an idiot (probably not so wide of the mark). "No, I'm not a masochist."

If I'd been less of an idiot I would have asked her how you say that in Icelandic.

Poldark continues on BBC One, Sundays at 9pm.