It has been dubbed The Avengers In Cardigans - no thanks to the multiple odd-coloured woollies worn by the cast of The Imitation Game as part of their recreation of Alan Turing's life.

Keira Knightley, face of Chanel, long-running star of the Pirates Of The Caribbean franchise and generic Hollywood A-lister, wanted to make sure she got the ugliest knit of all.

In fact, as director Morten Tyldum recalls, the actress had agreed to take on the part only if he promised "not to make her beautiful".

But "my face is always my face", the English actress says with the hint of a pursed lip turning into a sigh. "Whether people think it's too glamorous or not... that's what it is."

Knightley, 29, plays real-life mathematician Joan Clarke in the film co-starring Benedict Cumberbatch. As the almost-wife of Benedict's Turing, she plays the inspiration to the inventor of the modern computer and also comforter to the cryptologist extraordinaire who cracked the German Enigma code during World War II.

In the film - as in real life - Clarke had agreed to marry Turing even though she knew he was gay.

"I think people do choose companionship over romance," Knightley muses about her character.

"Particularly for that time period, when married women were giving up everything else and being chained to a kitchen sink.

"I could see her going for that for the friendship and the work and the chance to do what she wanted to. I could see how she could make it work."

What resonated in the actress, indeed, was this spark in a woman who wanted to claim her rightful place in the world of men.

"I liked the way she dealt with things. Even though there was massive prejudice against her, she wasn't a bull in a china shop," Knightley continues.

"She very much understood how she could work the system - which was almost to be pure sunshine.

"What she was really fighting for was a place at the table and equal pay. I thought that was equally fascinating because that's at the centre of the feminist movement.

"That was 1943 - the fact that equality still hasn't happened yet is still astonishing."

Today, Knightley is at the top of her own game, commanding no less than US$6 million (S$8 million) a picture, having dashed through blockbusters ranging from the Pirates franchise to Pride & Prejudice (2005) and Love Actually (2003).

Still, the figure is nothing compared with the multi-million packages her male colleagues take home.

The daughter of an acting couple, Knightley made her debut as a teenager in the 2002 sleeper hit, Bend It Like Beckham. Thirteen years into the business, she still has a few more things to say about power dynamics and gender discrimination.

"I think it's easier to talk about it today," she says. "There's got to be equality on both sides too. The number of guys who are friends of mine - who choose to stay at home and look after kids and get looked down on - it's shocking. The gender imbalance works both ways."

One is tempted to link her words to her own relationship to her indie musician husband, James Righton, with whom she is expecting her first child.

Knightley herself is upfront about it.

"It's great for men, obviously, that they can come to the table to talk about it. My husband says, 'I'm not a d***head, of course I'm a feminist too.'"

One suspects the actress' recent stance has come as a result of the side effects of fame via unwanted attention on her body - in the last decade demonstrated through "well-meaning" efforts by studio executives anxious to enhance her bosom on film posters.

Last September, Knightley decided to put an end to the obsession once and for all, creating the controversy that would finish off all other controversies. Posing topless in an untampered photograph on the cover of Interview magazine, she outed her assets publicly, protesting that "women's bodies are a battleground and photography is partly to blame".

At this interview, in a black tailored dress - draped over by requisite if stylish cardigan - the actress is completely covered up.

She is, however, more than happy to mouth off as she pleases.

She openly admits to enduring feelings of being an outsider in the very industry she works in.

"Have you never really felt like an outsider? Have I felt like one?" she asks rhetorically, echoing a question from a reporter quoting the theme of the movie.

"In every circumstance, differently... in this circumstance, obviously, very obviously. Very much an outsider, right now," she smiles adamantly at the row of inquiring reporters, then shudders awkwardly for apparently having just over-shared.

She speculates about the Pirates franchise - the next instalment of which she has passed on.

"It feels like something I've done already. I've been fortunate enough to have a choice, people were great and I'm sure the movie will be great."

Finally, she talks about why The Imitation Game was made, rattling off almost non-stop on a long speech.

"It's important we addressed the notion of prejudice in this film. The idea that you can be destroyed because you love a person of the same gender as yourself is shocking. On a personal level, that was why all of us were so passionate about getting this story out into a wider public," she says, anger on her brow turning into the tiniest glimmer of triumph as she moves from speaking to orating.

The face that has launched a thousand perfumes, that has been the distraction of boys and men from their rightful duties in life, that has been unmade and remade for each new incarnation on the screen - is luminescent with anger, joy, almost-perfect make-up, sweat... and a more mundane thirst.

"I believe art has the power to change things in general, that is the point of culture - that different cultures can explain themselves... my words aren't even making sense," Knightley continues.

"God, I need a cup of tea."