"I'm making a hot water bottle, I'm freezing" shouts Helena Bonham Carter. She continues bellowing cheerfully over running taps and lots of clanking. "I need to head off to work in a bit, but I've got to pick up my daughter first - Christmas holidays…" something metallic crashes. "Oops!"
We are in the Belsize Park house, in north London, that she shares with Nell, 10, and Billy Ray, 15, her children by director Tim Burton (the couple famously lived in adjoining mews houses). They split in 2014 - 13 years after meeting on the set of Planet of the Apes - and she refers to him easily as "my ex".
Like any single mother, Bonham Carter's priority is to put her children's needs over her work. Unlike most mothers, however, her acting career is still stellar at the age of 52.
She is wildly versatile - one moment the saintly matriarch in Charlie and the Chocolate Factory, the next lunatic witch Bellatrix Lestrange in the Harry Potter series. She's played psychiatric patients - in controversial film 55 Steps earlier this year, about a woman who campaigned against antipsychotic drugs - and the Queen Mother in The King's Speech (for which she won an Oscar nomination).
Her next role is another royal portrayal, as Princess Margaret in series three of acclaimed Netflix series The Crown.
"Everyone has such a particular idea of Margaret, it's very daunting," she says, "and I don't really look like her. But like the Queen, no one really knows what they're like privately, so you can make your own choices."
Her way into the role, she explains, was to research the real woman through those who had known her. "I did manage to speak to lots of good friends of hers, who really loved her. She was complicated. Being well known and vulnerable - or just human - is quite a tricky combination."
For the first two series, young Margaret was played by the brilliant Vanessa Kirby. Was it tough to take on a role owned so completey by someone else?
"I think we're so different, Vanessa and I..." she begins. "I certainly didn't base my approach on hers. But there are many portrait painters, many brilliant ones, and they'll paint the same person very differently and shed a different light."
Seemingly aware that she is in danger of veering into luvvie-dom, Bonham Carter reins herself in. "I feel like I've got to know somebody, retrospectively," she adds. "Of course I might have got the wrong person altogether!"
A veteran of high-pressure film sets, she has found the TV experience smoother. "Netflix is so fantastically generous with their budget, it's a very un-stressful job," she laughs. "It's very well run, it's very graceful… a bit like the Royal family."
The series isn't due for release until 2019, but fans can currently enjoy Bonham Carter's upper-cut tones in bestselling video game Call of Duty - more known for its violent shoot-em-up action than its British thespian quotient.
She plays Madame Mirela, a "fake fortune teller," alongside characters voiced by Charles Dance, Kiefer Sutherland and Brian Blessed.
"I have to admit, I didn't even know what Call Of Duty was - that's how out of it I am," she says. "It's about zombies going into…umm.. let me see what it says here. 'A new Black Ops 4 zombies adventure in the middle of the night…'" she reads aloud, cheerfully.
Listening to the woman best known for playing aristocrats discussing zombie attacks is slightly peculiar, but she is game. Clearly, for Bonham Carter, this is just another role to have fun with, although she has said in the past: "The challenge is to find something we all like doing and to get the children away from the screens, like iPads,"
"I'll do anything where there's good writing and good character," she explains. "I really liked Call of Duty because it was such fun and freedom - I didn't even have to get dressed up!"
She regularly uses the word 'fun' - especially when it comes to describing her award-spangled career.
"That's kind of why I act in the first place," she says, "to get away from reality, which can be a bit on the dull and limited side - so yes, acting is total fun. It's dress-up."
Her own reality, growing up, was a diplomat father, a psychotherapist mother, and a great-grandfather who happened to be Prime Minister Herbert Asquith. Combined with her outré fashion sense (Vivienne Westwood, pantaloons, stork's-nest hair) and reported friendships with establishment figures such as the Camerons, it's no wonder that for many people, she embodies a certain kind of posh, eccentric Britishness.
She, however, seems baffled by this.
"I don't spend much time thinking about what other people think. But also a lot of my career was taken over by Tim, my ex, and his films were certainly not British," she says. "I've done lots of different things, lots of different accents and nationalities. My name sounds very establishment, doesn't it?" she acknowledges, "but then, my mother is half French, half Spanish, so half of my family couldn't be more foreign. More was made of my posh Englishness when I was younger, because less was known of me. But I'm not that posh."
Besides, she adds, "It's none of my business what other people think of me, really - part of being famous is letting go of other peoples' opinions."
Surely one would have to be superhuman not to care at least some of the time?
"It depends on the day - there are times when I resent fame," she concedes. "Particularly when I'm with my children, or having a bad day. There are also times when I feel it's a very small price for a very privileged life."
Bonham Carter is equally straightforward on the subject of ageing – briskly dismissive of the 'after 40 it's all downhill' Hollywood view.
"Well, I turned 50, and then I'll turn 60 – and the more you do, the more confident you get, and the more discerning," she says. "There's such a consciousness about ageism [now], and for my daughter, it'll be even better - it's such an exciting and dynamic time in which to age."
Will she continue acting into her eighties?
"The problem is, you're so dependent on other people wanting to employ you, and I can't predict their taste," she shrugs. "Often, the thing you don't feel that passionate about - or a tiny role - is a hit, and you get something else because of that. Bellatrix had about 50 lines, spread over five years. But that role was definitely an advertisement for future parts."
Her portrayal of the witch hell-bent on killing Harry Potter was a masterclass in evil. "I went with the idea of a sociopathic child - if you're going to play a baddie and you can make them funny, kids are going to be less scared," she explains. "And I love the fact that she's so naughty," she adds. "I did think, 'I'm not a natural sociopath' but I have played a few, and I love it."
After all this time, she still adores pretending to be someone else. "Yes, though it depends what time of day you're doing it," she exclaims. "When you're woken up at 5.20am to get ready, and you're not used till 10am and you're already knackered, then you're like, 'Oh, that's what we're being paid for: waiting for everyone else to do their jobs, so you can do yours. And you must do it brilliantly," she adds, firmly.
Athough the adrenalin of theatre work has appealed in the past, she says, "one day I think I might again, but in all honesty I find it so anti-social when you have children. I wouldn't see them. Though a few matinees a week would be perfect."
That's what she loves most about playing Princess Margaret.
"The Crown is so family-friendly. We had a few weeks away filming, but on the whole, it's in England – so I get to have my cake and eat it."