As a three-year-old, Alicia Vikander would sometimes sleep in the wings at the Royal Dramatic Theatre in Stockholm, where her mother was a regular on stage, performing classics by Shakespeare and Moliere.

She recalls one moment when she woke up to see her mum passing through a set of gates. "I think it might have been in Twelfth Night and she suddenly slams the door; I thought she had gone for ever," says the 26-year-old. "I think I had quite a big breakdown at the time."

In metaphorical terms, the young Vikander is this year set to pass through a set of gates all of her own. By the end of 2015, she will have gone from rising talent to bona fide superstar. The actor, who first caught the eye of the English-speaking world in Joe Wright's stylish 2012 adaptation of Anna Karenina, has no fewer than nine films readying for release - famous directors are clamouring to work with her - with at least six already scheduled to hit cinemas this year, the first of which, Testament of Youth, has already drawn a clutch of critical plaudits.

The film is based on the 1933 book by celebrated writer and fervent pacifist Vera Brittain, which stands as one of the few memoirs of the Great War published by a woman, recalling with studied precision the people she lost, including her first love, Roland Leighton, brought to life in the movie by Game of Thrones star Kit Harrington.

"When I read the book and the script, it felt like she could have been a girl of my age at this time, now," says Vikander when we meet in a chic London hotel.

"Then, suddenly, a few more lines down the page it's a woman who cannot get on the train without a chaperone. It describes when she touched fingers with this young boy she fell in love with, and how they held hands for the first time after they'd already met 10 times.

"It's another time and shows the journey that women have come along over the last 100 years. So it was a part I really, really wanted to play. I was so happy they took a leap of faith and trusted this Swedish girl to play a British icon."

She tackles the part with aplomb, capturing her subject's pin-sharp intelligence and steely intransigence - Brittain refused to toe the line, battled vehemently for her place at Oxford then risked her hard-fought literary future to care for the wounded at the First London General hospital in Camberwell and at the military camp, Etaples, in France. Like her character, Vikander is bold on screen, brash at times, and thoroughly committed to her cause.

During her research process, Vikander met Brittain's daughter, the politician and academic Shirley Williams, for tea at the House of Lords. "I was so daunted," she tells me. "I was shaking. I think she said something like, 'You're Swedish and you're playing my mum.' I thought, 'Ah, that's a good start!'

"But we had a good chat and she's an extraordinary woman. I was really nervous, but I could definitely see where she came from. It was a big deal when her own kids came and visited me on set; they have seen the film and are happy."

What specific insights did Williams share with her? "She said her mother was quite cold and didn't send out any humour. I said that even though things happen to people, humour is still a human emotion, but she said her mum didn't really have that."

Vikander notes that her most useful research tool was Brittain's set of published letters because the memoir, though insightful, was written when Brittain was in her 30s. "It was a woman looking back at the woman she was, and I think we all know that if we look back on ourselves after 10 years we'd have a different view.

"So the letters she wrote to her brothers and her family during the war were her accurate words from that time, and gave me a sense of another woman, a younger woman, and that helped me a lot."

Vikander was surprised at their content, at Brittain's refusal to compromise her opinion, even when writing to Roland. She also says she was deeply affected by the most painful moments in Brittain's life. The actor says that when she first read the script, the scene in which Brittain hears of Roland's death felt like it might have been fictionalised. But the truth was there in Brittain's own words.

"I did think they'd pushed the story," she concedes, "especially when Vera hears that Roland is coming back for Christmas and she gets the phone call and he dies the day before their wedding day. That feels very much like a film moment but that was what happened.

"I read that letter I don't know how many times because it is just heart-breaking. It's him saying he is coming back home. 'I'm on the safe side and I'll see you in just a few days and when I see you you'll be my wife.' They were his last words to her. It is such a beautiful story and I am so lucky."

BREAK

As the cliche suggests, Vikander's fabricated that luck herself. She is an uncommonly accomplished actor, as anyone who's seen her feature debut in the Swedish film Pure, or the Danish movie A Royal Affair, will testify. Her performance in Pure earned her a Guldbagge Award (think of it as a Swedish Oscar).

Vikander was born in Gothenburg. Her father, Svante Vikander, was a psychiatrist and her mother, Maria Fahl Vikander, a prominent stage actor. "Growing up, it was just what Mum did. I remember when I was 13 or 14 she was playing a translator who works in court for war victims. It was a monologue and she becomes their voice. She was quite brilliant in it, and I remember thinking it was very intense."

Though Vikander is a serious actor and a fairly reserved subject, her interview is punctured by moments of sharp levity. She says performing is in her blood and, at the age of three, Vikander pestered her mother into enrolling her in ballet classes. "I think it was because I liked the tutus," she laughs, "then I always ended playing a pirate or a baker in the end-of-term reviews!"

Still, she eventually fell in love with dancing and spent nine years at Stockholm's Royal Swedish Ballet School, emerging at a professional standard, before surrendering that dream in a bid to pursue an acting career. She says she simply did not have the same passion as those around her.

"I realised that I was jealous of the girls in my class because they had a passion for ballet that was bigger than my own," she explains. "They could be up from 5am doing an extra barre class because they thought it was fun.

"I really loved being on stage and performing but I did it because I was competitive and I wanted to be up there performing, but I was embarrassed about how I felt about their passion. Now, with acting, I understand exactly that passion, because I want to stay up all night researching the roles. It's a neverending source of love."

That love affair is in full swing and Vikander says her father plays a key role in her film choices, reading every script and offering sage advice. Indeed, her father's interest in science-fiction and fantasy - he was reading Tolkien's work to her when she was seven years old - has proved especially useful when researching two of her forthcoming projects, Ex Machina, the directorial debut from screenwriter and novelist Alex Garland, and Seventh Son, a sprawling, rather overblown fantasy from Mongol director Sergei Bodrov.

"I loved Mongol and I wanted to work with the cast, like Julianne Moore and Jeff Bridges," she says of Seventh Son, which is set for a March release. The fantasy epic was also her first foray into English-language filmmaking, though problems with the film's execution saw Anna Karenina released first.

In Ex Machina, meanwhile, which opens this month, she is reunited with her Anna Karenina co-star Domhnall Gleeson. "We are already connected and we knew our passion together is amazing so we could go deep and do proper work instantly, which is great. He is a brilliant actor."

She will also provide support in the action thriller Son of a Gun, which is scheduled for release at the end of this month. "I play a fierce young girl who lives in Australia illegally and she is the love subject for [actor] Brenton Thwaites. It's a thriller-style heist movie."

The action continues this summer in the much higher-profile Man from U.N.C.L.E., in which director Guy Ritchie reboots the 1960s TV show for modern-day cinemagoers. Starring alongside Super-Man star Henry Cavill, Hugh Grant and The Lone Ranger's Armie Hammer, Vikander plays the female lead, Gaby Teller.

"She is a car mechanic in East Berlin who needs to go on a mission to relay some information and she must pretend she's a housewife," Vikander explains. "But really she's very much a tomboy and doesn't feel comfortable wearing the dresses that are picked out for her!"

Vikander then slips from 20th-century action to 16th-century romance with Tulip Fever, which is adapted from the Deborah Moggach novel by acclaimed playwright Tom Stoppard. "It's fun paced. It's a tough story but it has a lot of humour."

She plays a young woman who falls in love with an artist (played by Spider-Man supporting actor Dane DeHaan), who's commissioned to paint her portrait. "It's a difficult genre to find the balance, but I'm surrounded by Christoph Waltz, Judi Dench and Zach Galifianakis. I got to work with amazing people."

She also works with amazing people on Light Between Oceans, on which she has just finished filming with Blue Valentine director Derek Cianfrance. "I spend a lot of time with Michael Fassbender, which was wonderful.

"We play this married couple and the first half of the film is spent with those two on an island taking care of this lighthouse so it's quite a closed drama at the beginning." They then discover a baby abandoned in a rowing boat, "and then the story opens up and things happen".

Vikander has also shot the film Chef, which is written by Eastern Promises and Peaky Blinders scribe Steven Knight and shot by August: Osage County director John Wells with an all-star cast. The film she embarks on next, however, might just prove her most challenging project of all.

She has just started preparing for The Danish Girl from The King's Speech and Les Miserables director Tom Hooper, in which she stars opposite this year's Oscar-favourite and last week's Herald Magazine cover star Eddie Redmayne, the pair playing artists Lili Elbe and Gerda Wegener. Based on a true story, Redmayne's character, Lili, is the first identifiable person to have undergone a sex change.

Again, Vikander's father proved a vital source. "My dad has done a lot of work with transsexuals so he proved very helpful with this film," she says. "It's also one of the most complex love relationships I've read in a script, and it's also about a couple of people who dared to do something extraordinary.

"They were pioneers and he was the first one who went all the way and decided to go through a [sex] change." Lili Elbe was born in Denmark in 1882 as Einar Mogens Wegener before the pair became lovers. "It must have been quite a terrifying thing, medically, but also because there's no reference. Nobody had done it before."

It sounds a challenging film but she will no doubt shine alongside Redmayne. By the time the movie hits cinemas, either at the end of this year or in 2016, you can be sure that Vikander will have passed through the gates and emerged as a household name.

Testament of Youth (12A) is released on Friday.