Fifty Shades of actor, model and musician Jamie Dornan

But that's not what Jamie is referring to. In fact, the role that the Co. Down actor is most proud of couldn't be farther from the sadomasochistic Mr Grey.

"Becoming a Dad is the best thing that ever happened to me - to us - and it's an extremely joyful situation," he says excitedly. "Every day seems to get better and I know it's the most important role in my life. It's an intense role."

Indeed, when his daughter was born last year, it was that start of a rather intense period - the baby arrived on the eve of Jamie was due to begin filming 'Fifty Shades of Grey' in Canada.

"We had our baby three days before we started filming, so you can only imagine how mad a time that was," he says. "Relaxing was changing diapers and having a little baby vomit on my shoulders and waking up four times a night. That was how I relaxed when I was doing the shoot. It was pretty full-on."

If things were full-on then, one can only imagine how it will be after the release of the hotly-anticipated movie next week. The subject of intense speculation ever since it was announced in October 2013 that he had landed the role of Christian Grey, Jamie's performance will be eagerly scrutinised by fans and critics alike.

Although he's not especially worried about being pigeon-holed for this part, Jamie admits to being very insecure and anxious about how devoted readers of the hugely-successful 'Fifty Shades of Grey' will respond. He will be at the Berlin and London premieres - but confesses that he's really not looking forward to it.

"There's no one really like Christian Grey. George bloody Clooney probably comes the closest!" he laughs. "I almost don't want to put this out there - but I fear I'll get murdered, like John Lennon, by one of those mad fans at the premiere. A lot of people are very angry that I'm playing this character. I'm a father now and a husband and I don't want to die yet. What am I doing, predicting my own death on the red carpet?"

It's hard to tell if he really is this insecure or if this is just typical Irish self-deprecation. Jamie hails from Holywood, Co. Down - the same town as world number one golfer Rory McIlroy. Indeed, the pair were seen hanging out together as recently as last November at a pro-celeb charity championship in Scotland.

"I think people consider Irish people in general to be very down on ourselves," Jamie muses.

"I have a group of mates from Northern Ireland who, to put it mildly, never let you get carried away. We're quite harsh on each other, but I think it comes from a place of love. Maybe that's what helps me do this for a living."

The youngest of three, Jamie is descended from Methodist lay preachers on both sides of his family. His father, Professor Jim Dornan is a famous obstetrician, who shares his son's passion for acting. His mother, Lorna, who was a nurse, died from pancreatic cancer when Jamie was 16.

"There's a massive element of me that's fractured from losing my mother so young," he admits. "Not that I'm some kind of broken bird, but I am drawn to characters that are wounded."

After dropping out of Teeside University in Middlesbrough in 2001, an 18-year-old Jamie entered Channel 4's 'Model Behaviour', reaching the final round of auditions in Belfast. Though he failed to make the line-up for the show, the boost to his confidence prompted a move to London to pursue modelling. A successful career was to follow, with Jamie landing campaigns for Armani, Dior and Calvin Klein with the likes of Kate Moss and Eva Mendes.

Despite this experience, the man who was once dubbed 'the golden torso' by the 'New York Times' insists that he is as full of insecurity about his image as the next man (or woman). "I think I am like anyone, I have massive hang-ups about my physical appearance," he says. "I was a very skinny kid, but I played a lot of sport. I played rugby and took it very seriously. It's a very physical sport and even more so these days than it used to be.

"I was always fighting against stuff when I was a kid. I always felt skinny and small. Now, I'm 32 and getting way too old to play rugby, even if I wanted to. I have the same insecurities when I was a kid and when I see an image of myself, all I see is this skinny kid and I don't like it."

But surely being cast as the perfect physical specimen that is Christian Grey must have put any doubts he had to rest?

"No matter how many times you get filmed with your top off and the photographers are saying 'oh, you look great, add more oil', and all that, you have all these things ingrained in your head - insecurities about yourself. All the people in the world saying stuff like this isn't going to alter that," he says. "I only had four weeks to work out for this role. I would have liked more time. But like I said, I don't think I am ever going to be happy with how I look."

One area where Jamie is secure and happy is in his marriage to Amelia Warner. Singer Amelia, who performs as Slow Moving Millie, was previously in the spotlight due to her romance with Colin Farrell over a decade ago. Although it's often reported that the pair were briefly married, she recently dismissed this, saying that they did have a beach ceremony in Tahiti but they both knew it wasn't legally binding.

She was later introduced to Jamie by mutual friends in LA and the pair were - definitely - married in England in April 2013. Last year they welcomed their baby girl, whose name they have chosen to keep private. Jamie is vocal about the importance of romance in relationships - his own as much as anyone else's.

"My whole thing about Valentine's Day is, it shouldn't take a night like that to be romantic. You should be romantic all the time with your girlfriend, your wife, your partner, your boyfriend. It shouldn't just be one night a year. We should be making an effort and doing it all the time.

"Some guys are really useless about Valentine's Day but I think I have always tried to make some conscious effort to do something romantic. Now that I'm married, I feel that even more so. You have to keep the romance alive, especially when you have a baby."

So will he be taking Amelia to see 'Fifty Shades of Grey' next week?

"I think if you are with your girlfriend and she wants to see it, I think there can be a benefit after you get home from taking someone to see it! That makes sense to me. We won't be going to see 'Fifty Shades of Grey' on Valentine's night!"

Interestingly, he says that he sees 'Fifty Shades of Grey' more as a romantic story rather than as the "Mummy Porn" label that has been attached to it.

"Romance novels have been written plentifully for an abundance of years and this is why I get defensive of the story itself, the actual love story behind it. Behind all the BDSM (bondage, domination, sadism, masochism), there's a really great love story and I really think that's what's resonated with so many readers. If people want to call it 'Mummy Porn', that's their prerogative. Whatever.

"It's not a term we used in making the movie. If anything we deliberately avoided it. We're trying to prove it's a love story that has a certain kind of sex involved and it's essential to telling the story and a big part of their relationship. But we definitely didn't set out to make a movie and put it under a bracket called Mummy Porn."

Jamie lights up when our conversation moves on to music. For a few years, he was in a band called Sons of Jim and his enthusiasm for music seems to far outweigh his interest in modelling or acting.

"I am such a fan of music and I love it so much, but being in a band takes up so much time and energy and you have to be wholly committed. I didn't feel we were that good as a band and that is not a good energy to have. We did it for fun and then people wanted it more than we wanted it ourselves and it sort of got beyond us. I think you have to have a sort of arrogance and a belief that you are the best, to put stuff out there that is better than other people's music. I definitely, definitely didn't have that.

"I'm very happy being a music fan. I still love it and I play. I knocked around on the guitar for an hour-and-a-half yesterday and my wife wasn't pleased with it. My baby danced to it for a while, but that's not saying much. I still enjoy it, but I am far safer being a fan of music than a performer."

And what of his own performance? Jamie has already signed on to make two more movies, based on the remaining books in the 'Fifty Shades of Grey' trilogy, but the success of the first will likely determine where his career goes next.

"One of the main reasons why I have chosen to be an actor - and it's a pretty strange way to make a living - is that it can be whatever you want it to be and there's so much variety in it. I don't want to get typecast. I want to have a varied career. In the last couple of years, I have played guys who were psychopaths or sociopaths and I don't want to play guys like that my whole career. They are so far from what I consider myself to be. I love the idea of doing comedy and of mixing it up and keeping things interesting for myself."

Additional reporting by Gillian Fitzpatrick

Pictures: Adam Whitehead/The Daily Telegraph