Cynthia Nixon on Sex and the City, beating cancer and on coming out gay

Does she think that the series put pressure on women to look a certain way? “I totally do,” she says. “Sarah Jessica says that when she’s out with Matthew Broderick and they walk past a woman in the street dressed in a certain way – particularly with the heels and everything – he says [sinister, accusatory voice] ‘YOU did that!’

“And I wish that women would understand – or understand more – that it’s a fictional TV show. No one should be expected to walk around looking like that in life – other than on the red carpet! But what I would say is that high heels are high heels – if you buy expensive ones they’re OK and if you buy cheap ones, you won’t last an hour in them.”

She is poised and gazes at you with an open-eyed, alert expression that, coupled with a courteous reserve, lends a certain business-like quality to proceedings. Nixon is a pro and can don the heels and tight frocks when it is demanded of her. Are there times when you actually enjoy dressing up? “It’s all right,” she says. “It’s better than a kick in the head.”

Nixon wants to be as normal as possible, using public transport in New York, where she was brought up and still lives, and educating her three children at state schools. Her wife, Christine Marinoni, was a state school advocate – which is how the two women met.

Nixon with her wife Christine Marinoni

Before going out with Christine, Nixon lived with Danny Mozes, a classmate from high school. They split in 2003 and have two children together, Charles and Samantha. Christine gave birth to a son, Max, in 2011 with the help of a male friend, and all parties share parenting duties.

Do you find it easy calling Christine your wife? “Yes! She protested a lot at the beginning and wanted a more gender-neutral term, like ‘my spouse’. I said, ‘You think I’m doing that, you’re crazy!’ Marriage was never a goal of mine. I was with my boyfriend for 15 years and we never got married. But it seemed like Christine and I did fight really hard for it and we had a lovely wedding [in 2012]. Why wouldn’t I have done it?

“I had never dated a woman before or even kissed a woman or anything, and so when we started seeing each other, Christine kept waiting for the other shoe to drop, for me to panic about what this would mean – to my career or to myself – as if somehow I just hadn’t noticed that she was a woman. And then she met my mother and that was when she stopped worrying about it.”

Her latest role is playing poet Emily Dickinson in A Quiet Passion (in cinemas on Friday 7 April) by the esteemed British director Terence Davies. Viewers are made to feel all the raw injustice and loneliness of what it was like to be a woman in the mid-19th century, struggling to create without encouragement, recognition or support.

It’s an intense performance (her death scene is definitely not one of going gently into that good night), reminding you of Nixon’s acting credentials and why she is garlanded with awards.

After debuting on TV in 1979, aged 12, her first film role came in the following year’s Little Darlings. She made her Broadway debut at the age of 14, in a Lincoln Center revival of The Philadelphia Story. As a teenager, still studying, she acted in two substantial overlapping plays on Broadway, both directed by Mike Nichols.

It is quite rare for a child star to make the transition to a successful adult career. Her late mother, Anne Knoll Nixon, was a TV executive/ writer who had wanted to act herself (she was a classmate of Paul Newman at the Yale School of Drama) but diverted her ambitions into becoming a coach to help her daughter.

Cynthia’s mother died of breast cancer in 2014, at the age of 82, and she herself is a breast cancer survivor and spokesperson. Particularly because she is an only child, I suggest she must miss her mother dreadfully.

“I don’t, funnily enough,” she says. “My connection to my mother was so complete, and she had a really good life and lived to be a good age. There are moments, of course, when I think ‘Oh, she would love this.’ Like I would have loved her to have seen this film because she brought me up on Emily Dickinson. But I don’t feel there is unfinished business.”

The lack of resolution lies with her father, Walter, a radio journalist who died in 1998. He split from his wife when Cynthia was six. “He was a very troubled person. I think he was manic depressive, honestly,” she sighs. “I was as close to him as he was to anybody, but there are all sorts of things that I didn’t understand about him and that he didn’t understand about me.”

Are you rebellious? “No, I’m a very obedient person.” Do you despair of your obedience? “Sometimes. When I was growing up I felt like I wasn’t defiant and I would just go along with things, but it doesn’t mean I’m less interesting.”

Nixon’s mother was always thinking of parts her daughter could play when she was older. Early one morning, they were reading Sophocles’s Antigone – how very New York intelligentsia – and Cynthia fancied the lead part of the stroppy, independent-minded daughter of Oepidus rather than the pliant, rulefollowing sister, Ismene.

“No, no, no!” her mother said, “You’re not an Antigone, you’re an Ismene.” “Well,” her grown-up daughter says now – a smile spreading – “I actually turned out to be an Antigone, even though it’s not in my nature.”

A Quiet Passion is in cinemas on Friday 7 April