Tilda Swinton tells Alison Jones how motherhood is a learning experience for both parent and child...
"I have now made a film they can legally go and see - a U, even though I am in it, and they have told me they don't want to go and see it."
Tilda Swinton, undisputed queen of the British indie scene seems resigned to her twin children's indifference to her work.
"They understand what I do. They are very tolerant and slightly diffident about it. It takes me away from them and why would they be that interested in anything that takes me away from them?"
Currently to be seen as the White Witch plunging Narnia into a winter so bleak Christmas never comes, it is a rare foray into family film territory.
She admits it was an uncomfortable fit, her usual m>tier being challenging art house quirk.
A small role opposite Tom Cruise in Vanilla Sky and an androgynous turn as the Angel Gabriel in Constantine are the closest the slightly other-worldly actress has come to mainstream, until The Lion The Witch and the Wardrobe.
After spending weeks in New Zealand working on the $180 million Disney behemoth, she said that returning to small budget offerings such as Jim Jarmusch's Broken Flowers and festival hit Thumbsucker - playing this week at the Mac - was "like going home.
"All I can think of is how familiar and how healthy that experience is to me."
In Thumbsucker she plays Audrey Cobb, a mother struggling to cope with her teenage son's growing pains and her own disastisfaction with her domestic role.
"People say to me these days 'you always play mothers' but I've only done it three times."
Though she will herself eventually be the mother of a teenage boy - "I hope Thumbsucker isn't a dress rehearsal", she jokes - she is reluctant to draw parallels between her own experiences mothering seven-year-olds Xavier and Honor and those she portrays on screen.
"I am so not that mother. (Acting) is an opportunity to be a different mother every time. Everyone tries their best. It is not a very easy job."
What is obvious is her great joy at seeing the stages of her children's life unfold and her amusement at their entirely natural and unselfconscious self-obsession.
"We were talking about birthdays and I broke it to them that I wasn't actually going to be eight next birthday with them. They were really sulky about that. They suddenly realised that I had actually been alive before them.
"They really hate it when I talk about 'before you were born....' I do sort of know what they mean because an enormous part of you is born when they are. I hope there are all sorts of new selves coming."
In Thumbsucker, adapted from a novel by Walter Kirn, Audrey is almost as emotionally adrift as her son Justin, who is clinging onto the childhood comfort of thumbsucking to soothe his fears.
His mother seems disconnected from the family, bewildered at how she came to be a 40-year-old woman with a son old enough to go to college.
"I think this is a coming of age story that is about an entire community," says Tilda.
"It is about 40 year olds thinking they are 17 and several 17 year olds who think they are 38. There is also an 11 year old who seems about 64 .
"It is about the way in which our consciousness and our spirits grow or don't grow or resist growing or long to grow.
"It is so much more important than this idea of some sort of schematic development we are all supposed to be a part of.
"The idea that there is some rigid shelf of success, some foothill that we are going to reach when we are going to become 'grown up', to 'make it'. That is anathema to me and I am realising the longer I live, that it is truly anathema to everyone. But we are still sold it, I suppose, because it makes us buy things, to get their secret, acquire a rung..."
Motherhood has certainly made her feel more compassionate towards her own parents. Descended from one of the oldest families in Scotland - her father is Major General Sir John Swinton- they shipped Tilda off to boarding school where she was in the same year as the then Lady Diana Spencer.
"I think one of the great insights that comes when one has children is realising how little one's parents ever knew or do know. One forgives any attempt they still make to let you know that they know what they are doing. Obviously they don't, none of us do."
The actress seems as entirely released from the idea of convention in her personal life as she does professionally. Married to the writer and artist John Byrne, who is 20 years her senior, they live in the Scottish highlands, about as far from the celebrity hub as it is possible to get.
She mocks the idea that her film choices are part of a career plan, she is more attracted by the personalities involved "I'm fortunate that I keep meeting new people I want to hang out with."
Narnia will undoubtedly put her on the radar with the big studios but she sees her status as something she can use to get the small projects she is passionate about green-lit.
Her occasional dabble in what she dubs "industrial film making" is more a fact-finding mission for cinema's defiant outsider.
"I am infiltrating," she laughs. "Seeing what I can learn."