Little about the actor and sometime model Gwendoline Christie is strictly conventional: she describes herself as someone who sees a norm and wants to sprint in the opposite direction. Even so, in the hours before we meet, Christie has really outdone herself. The 40-year-old is just back from New York fashion week, where she stunned a Manhattan crowd silly by walking the runway dressed in a huge, floral, giant, rainbow-coloured... What was that thing, I ask?

“I like to think of it as a sexy sea cucumber,” Christie says. “It moved like an underwater creature. It was incredible to wear something that was the product of someone’s unbridled imagination.” The outfit (feathery, like a Sesame Street costume minus the headpiece) was made by the Japanese designer Tomo Koizumi, and judging by the reaction of Christie’s fans online it was a hit. For at least a few hours, their excited chatter about the imminent final series of HBO’s Game Of Thrones, in which she plays the warrior Brienne of Tarth, was put aside for discussion of the dress.

“Well,” Christie says, leaning back into a sofa, dressed plainly today in shirt, flared trousers and buckled shoes, “I was very entertained by it. It made me feel extremely present and stately. I’ve always found that interesting: clothes that make you feel more than yourself, rather than, as a woman, wanting to be diminished, wanting to take up less room. I’m interested in exploring the opposite of that – what it’s like to take up more room.”

Facebook Twitter Pinterest Christie modelling the Tomo Koizumi dress. ‘Why something isn’t the norm is interesting to me.’ Photograph: Steven Ferdman/Getty Images

To drastically distil a two-decade career, Christie has tended to take acting jobs playing either royals or royal bodyguards. Cast, straight out of a drama school, in a Declan Donnellan production of Great Expectations, she went on to play a Shakespearean queen for the director in 2007’s Cymbeline. This year Christie will play Titania in a Nicholas Hytner version of A Midsummer Night’s Dream. Between came the name-making bodyguard roles: an armour-clad protectress in Game Of Thrones and stormtrooper Captain Phasma in two of the Star Wars movies.

Appropriately, her conversational style is a little bit regent, a little bit rank and file. Christie’s diction is crisp, pronounced, underlaid by a queenly growl that comes from the back of her throat. Her laugh – the loudest in any room – would not be out of place in a military barracks. When Christie finds something funny she angles back her head and howls at the ceiling. She’s interested in accepted rules of behaviour, she says, and often feels tempted to bend or break those rules. “Why something isn’t the norm is interesting to me. How does something or someone not conform? Why? What is seen as wrong with not conforming? I’ve always been interested in that – I suppose from a very dull perspective of my own physicality.”

Christie is very tall, 6ft 3in in flats. She makes free reference to her height in conversation, though always with the little paperclipped hint attached, that this subject is “dull” for her, “something that in a not-very-interesting way tends to inform a lot of my life”. She first broke the 6ft barrier when she was 14, a schoolgirl in the South Downs. And that’s a lot of time, between 14 and 40, to be answering ironic public inquiries about the weather up there. Of course she finds the subject dull.

I didn’t fit that type, y’know? So I got interested in actors who transformed themselves, Marlon Brando, Tilda Swinton

Was she more of a conformer, I ask, when she was a kid? “Probably at primary school,” Christie says. “I probably wanted to just fit in. Schools are funny things. Any young person’s experience tends to be about trying to find some comfort in fitting in.”

She did not fit in. As a teenager Christie had offbeat interests, in performance art, foreign films – things not well catered for in rural 1990s England. She read a lot of imported fashion magazines. She has spoken in the past about being bullied at school. “I was incredibly lucky,” she says now, “that there was something inside me that just decided, ‘Fine. If I’m outside the party, then I’m going to have a party of my own.’” Christie laughs quietly, despairing of herself. “Because what else was I going to do? If you’re shut on the outside then you might as well enjoy yourself on the outside. Make the best of it.”

Facebook Twitter Pinterest As Brienne in Game Of Thrones. Photograph: Lmkmedia

Her father was a salesman and her mother a housewife. Christie left home when she was 18 to spend a year as a volunteer at Central Saint Martins in London, assisting the MA fashion design students. “That year changed my thinking, fundamentally,” she says. “Being around those people, those students, made my mind expand.” She wanted to act. “But I didn’t fit that type, y’know? Actresses seemed to me to be classically beautiful. At that time they seemed to be incredibly thin. It was just an aesthetic that I didn’t fit. So I became interested in the actors who transformed themselves, [Marlon] Brando, Tilda Swinton. Grace Jones really blew my mind. Such a powerful woman, who really didn’t seem to take on other people’s expectations. It was about her expectations of herself. That was monumental to me.”

In her early 20s she attended the Drama Centre London and was warned by her tutors, before graduation, that regular acting work would be hard to come by. They weren’t being cruel, in Christie’s opinion, only trying to be realistic. In a world of teeny-tiny male actors, being a 6ft 3in woman would limit her opportunities. As a graduate, jobs came in spurts. There was the breakthrough Cymbeline part, followed by the opportunity to play the devil in an ambitious production of Faustus at the Royal Exchange theatre in Manchester. There is a brilliant video on YouTube that shows Christie during this period of her life – high in the vaulted eaves of the Royal Exchange and about to rehearse a stunt in which she’s lowered into the auditorium on wires. She tries an ambitious flip on the descent, gets stuck upside down, and laughs that familiar laugh, shouting to nobody in particular: “I was trying something different!”

Facebook Twitter Pinterest Styling: Steph Wilson. Stylist’s assistant: Rosalind Donoghue. Hair: Jonny Eagland at John Frieda. Makeup: Andrew Gallimore at CLM. Producer: Emma Allan at Lemonade Productions. Dress, Roksanda. Photograph: Gustavo Papaleo/The Guardian

During this period of fitful work Christie was given some measure of financial stability by the writer and actor Simon Callow, a Drama Centre graduate himself. Callow has been one of the most important figures in her life, she says, the whole thing launched by fluke, off the back of what she calls “a misguided conversation-starter”. Callow had phoned the drama college, looking for a student who could do some part-time filing for him while he wrote a book. “I really liked the school secretary,” Christie recalls, “and I wanted to impress her. But I felt incredibly dull and like I didn’t have anything of interest to say, so for some reason I had taken it upon myself to lie and claim that I ‘loved’ filing. Which I didn’t mind. But I certainly didn’t love it. The secretary told Simon: ‘I’ve got just the person!’”

Simon Callow coaxed me out of my shell. He would shout at me about my lazy and disorganised mind, throw books

She went to Callow’s home for an interview, “pouring with sweat”, intimidated by his reputation and body of work. “How do you go into that situation not feeling intimidated? Maybe people do now, maybe millennials feel confident, I don’t know. Anyway, he answered the door and this kindness poured out of him.” For years Christie worked as Callow’s research assistant and his dog-walker, and the two developed a mentor-mentee relationship. “I suppose he coaxed me out of my shell when it came to being an actor. He would shout at me about my lazy and disorganised mind, throw books… At the time I was scared to say that I wanted to be an artist. I was scared of how that sounded. That it was naff, or a cliche, or corny. That it wasn’t realistic. Simon would say: ‘Be an artist.’ He came to my plays and gave me feedback. Which, sometimes, could be incredibly near the knuckle.”

Christie was doing all sorts at the time. She was plugged into the outsider art scene, and danced in music videos. She had modelled a little, once posing semi-nude and masked for a Goldfrapp record cover. She sang well, and would sometimes join her friend, the outre musician Patrick Wolf, on stage. At a gig in Berlin in 2011, Wolf told the crowd that Christie had just been cast in a weird-sounding TV show. “She’s been learning swordfighting and horseriding,” Wolf said, asking the audience if they had heard of this thing, Game Of Thrones? Some had, some hadn’t. Back then, it was a fairly niche series of fantasy novels.

“No one had heard of it,” is Christie’s memory. She threw herself into prep work, cutting her long hair for the first time, and hiring a boxing trainer to toughen her up. It would be her first proper screen role, at the age of 33. She cannot have had much faith in the programme’s longevity, or in her own continued employment, because even after her Thrones debut in spring 2012, she kept doing dog-walking shifts for Callow.

Does she remember feeling nervous about what her mentor would think of her doing a swords-and-shields show?

“Yeah. Hugely.”

What did Callow think?

Facebook Twitter Pinterest ‘No one was more surprised than me that people liked my character in Game of Thrones’ Photograph: Gustavo Papaleo/The Guardian. Coat, Roksanda. Pumps, Midnight 00.

Christie does an impression of the senior actor, camp, teasingly appalled, asking his classically trained protege: you’re doing sci-fi? She laughs herself giddy at the memory, wheezing: “How was he to know? How was anyone to know?” Before long, Game of Thrones was being watched by about 25 million viewers in the US alone. Add at least another 10 million in the UK and other territories: Christie’s first TV show was the TV show.

In the early series she had some wonderful scenes. There was a fight with a bearlike 6ft 6in baddie, played by Rory McCann, and a fight with an actual bear, played by CGI. Christie was able to show off her subtler stage instincts, helping develop an intriguing relationship between her own character, the forlorn Brienne, and a devil-may-care rival, Jaime, played by Nikolaj Coster-Waldau. “No one was more surprised than me that people liked my character,” Christie says. “I just assumed that, because she wasn’t a conventionally attractive woman, people wouldn’t get behind her. I’m overwhelmed that they did.”

Between seasonal Thrones shoots, on location in Northern Ireland and elsewhere, Christie was cast in the recent Star Wars reboot, appearing in two instalments as Captain Phasma, the stormtrooper who wore distinctive silver armour. I think the scriptwriters could have given Phasma a little more that was distinctive in the way of character; but Christie seems satisfied, and she says she “could cry” to have been given the chance to be a part of it all. Her sideline as a fashion model kicked off around 2012, after the intervention of Kate Moss, who met Christie at a party and offered her representation with her own agency. Christie later became one of the faces of Vivienne Westwood. And in 2017, Jane Campion cast her as a rookie detective opposite Elisabeth Moss in the second season of Top Of The Lake, after Christie wrote the director a fan letter. Again she played against type – the chaotic cop having an affair with her married boss, driving Moss’s self-contained character to distraction.

Facebook Twitter Pinterest In Cymbeline with Tom Hiddleston, 2007. Photograph: Alastair Muir/REX/Shutterstock

By the time Game Of Thrones was halfway through its run, some viewers, me included, began to wonder if the show’s writers were taking their eye off Christie. The character of Brienne seemed to be left dormant through too many episodes – standing in the background, glowering silently, while meatier material went to others in Thrones’s large central cast. Happily, as the show started to taper towards its end, Christie moved back into the thick of the action. There has been a fan-pleasing reunion with Jaime, a swordfight with a child assassin, a romantic subplot involving a flame-haired marauder called Tormund Giantsbane – standard Thrones stuff. What will come next for her, in the show’s final episodes, is a mystery. You’d be as well asking a spy to reel off state secrets. The cast have been well drilled not to reveal spoilers, and bat off inquiries with ease.

They squeezed the orange. Every last drop of juice out of that orange! And just a husk was left behind

“It was just a lot, a lot, a lot. It was a lot!” Christie says of shooting the final series. Recently, when I met one of her co-stars, Kit Harington, he told me that the workload “seemed to be designed to break us... I remember everyone walking around on set towards the end going, ‘I’ve had enough now. I love this, it’s been the best thing in my life, I’ll miss it one day, but I’m done.’” Christie sits poker-faced while I recite this quote to her, seeing where it’s heading. Then she breaks out into a grin. “I agree with Kit. They squeezed the orange. Every last drop of juice out of that orange! And just a husk was left behind.”

Can she say some more?

“That character has changed my life. I feel emotional. I feel emoji.”

Which emoji?

“Tears straight down, and the scream.”

Christie is just as cheerfully evasive when I try to ask about her romantic life. She regularly appears in dresses made by fashion designer Giles Deacon, her partner for about the last five years. They sometimes trade Instagram endearments, and heart-eyed emojis, but she won’t be drawn on him. “Because I have a private life, Tom.” Instead we discuss the fashionable crowd in which she and Deacon move these days. Red carpets, intimate VIP parties. Having heard Christie speak about her youth, when she often felt like an outsider looking in, I wonder how it sits with her now – to be an insider looking out?

Facebook Twitter Pinterest Christie with (from left) Nick Grimshaw, her partner Giles Deacon, Kelly Osbourne and Kate Moss, 2018. Photograph: Marc Piasecki/GC Images

“I think the fashion world is full of people who didn’t used to feel they fitted in,” Christie says. But, yes, she takes my point. “There have been previous circumstances... where I’ve been told that I’m too niche to work with a company. And then, suddenly, that wasn’t the case any more.” I think she means: with Games Of Thrones a stonking hit, some unnamed fashion brand decided this 6ft 3in woman in her mid-30s wasn’t too niche to hire after all. “Which I found hilarious,” Christie says.

I suggest that she names the company. Call them out. Embarrass them a bit!

“No. Why? What would be the point of that?”

Facebook Twitter Pinterest In Star Wars: The Force Awakens. Photograph: Lucasfilm/Bad Robot/Walt Disney Studios/Kobal/REX/Shutterstock

So the lesson is out there, I say. That it’s worth looking at unconventional talent more closely. That it’s boring and lazy to think in terms of people or things being too niche. “They’ve learned the lesson by casting me,” Christie insists. “They’ve learned the lesson that we need to see some different things in entertainment, and that people need to feel represented.” She shrugs. She’s no good at being confrontational, she says. “Instead you support people. You support new people you believe in.” Like Tomo Koizumi, who made her wild fashion week dress. “There’s no point dishing out the negativity. Everyone’s only human.”

We talk about life after Game Of Thrones, which will start more or less as soon as we finish our interview. “Structure can be a blessing,” Christie says, recalling that when she first signed the contract, back in 2011, “I remember seeing how many years it could potentially be for. That seemed so far away.” Signing the endless contract was about the most conventional thing this determined eccentric had ever done. Out the other side of it now, with “no time constraints, no schedule clashes”, Christie says she looks forward to exploring a more chaotic existence again.

She gives an example, her recent escapades at New York fashion week. Before appearing in the oversized Koizumi costume, Christie was already taking up a lot of room, struggling to fit through doors, when she was asked: which shoes? Flat ones, or eight-inch platforms that would push her up to a height of about 7ft? “Anything that makes someone gasp,” she says, “even for a moment – it deprives their brain of oxygen and they enter a slightly different state. It’s an extraordinary thing. It was a boxing coach on Game Of Thrones who told me that.” Christie chose the platforms.

• The eighth and final season of Game of Thrones will air on 15 April on Sky Atlantic and Now TV

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