Of course, when her latest role is a queen who wants to be the fairest of them all and who seeks daily validation by talking to a mirror, it's an obvious line of questioning.

Taking her lead from Jack Nicholson in The Shining rather than Disney, Theron's melancholic Queen Ravenna is the villain of Snow White and the Huntsman, a dark revisionist fairytale in which she keeps Snow White, the answer and threat to her eternal beauty, imprisoned in her castle.

Perched by a grandiose fireplace in the drawing room of the real-life Arundel Castle in south-west England, 36-year-old Theron says she is unfazed by the ageing process.

''I like it so far, because in my 20s I had the fattest face you've ever seen in your life,'' the former model says. ''It looked like I'd swallowed a small child. That, thankfully, has gone away in my 30s.

''I have a beautiful mother and she has such a full life with other things that [looks are] not the focus. I feel lucky I was raised that way.''

While Theron is at the top of the tree in terms of Hollywood beauties, her looks are the least of her qualities. She is intelligent, articulate and her conversation reveals a sharp wit.

The director of Snow White, Rupert Sanders, describes her as a cross between Kate Moss and Margaret Thatcher. ''I just hear the Kate Moss part,'' Theron says with a wry smile.

Ultimately, the South African-born actor had to sacrifice her appearance in order to get ahead in her career.

She was all but unrecognisable in her signature role in Monster (2003), following her transformation at the hands of a make-up artist who altered her looks with splotchy skin, prosthetics and ill-fitting false teeth.

Theron played Aileen Wuornos, the Florida prostitute and serial killer executed in 2002 for murdering seven men. The performance won Theron an Oscar. So much for beauty.

Almost 10 years after winning her Academy Award, she has a realistic outlook on her success. ''I've never said at any point of my life that I thought I was that great an actor, or that I was that much better than anybody else,'' she says.

''I feel I've been given great opportunities and those come around very rarely, so I'm not jaded about that at all.''

Theron had to wait until recently for a role to match Monster, but her turn as a deluded alcoholic divorcee in last year's Young Adult failed to gain another Oscar nomination.

This year she has appeared in a double-bill of her most high-profile potential blockbusters, Snow White and the Huntsman and Ridley Scott's Prometheus, both shot at Pinewood Studios in Britain.

Describing the experience of shooting the films back to back, she says: ''I did have a couple of moments where I had to check in with my ego - because they were breaking down my spaceship to build my castle.''

The past couple of years of work have been fruitful but Theron's heart has been elsewhere. Last month, she finalised a two-year adoption process to become the mum to a baby boy named Jackson.

She has largely escaped the media attention surrounding other high-profile adoptions involving Madonna and Angelina Jolie.

After a 10-year relationship with Irish actor Stuart Townsend came to an end recently, some suggested it was surprising Theron didn't become a mother earlier.

''I'm not going to go into our relationship, but I always knew I would adopt - no matter what the situation my life was in,'' she says.

''So this wasn't like a last resort for me now that I'm a single woman. I just really knew I wanted to be a mum.''

The changes as a result of motherhood are already apparent in Theron. Her last words to me when we met a couple of years ago were, ''Can I bum a cigarette?''

It's the kind of terminology only serious smokers use.

With a clap of her hands, Theron laughs heartily at the memory. ''Trust me, I was as proper [a smoker] as they come. I realised one day I was going to kill myself,'' she says. ''I was never one of those sexy smokers. I've quit a lot; I'm a professional quitter. So, yes, my son definitely helped me maintain not smoking.''

The two arrived in Namibia last week for the filming of Mad Max: Fury Road, the Namib Times reported. The shoot relocated from Australia after being in limbo for more than two years.

The film's location will allow Theron to return to her roots - her father and mother, who will accompany her during her stay, were born in the country when it was part of South Africa.

Theron's co-star, Tom Hardy, who plays Max Rockatansky, says there is more action in the first 20 minutes than in the previous three films combined. That suggests a departure for Theron.

''Yes, it's huge, I've never done anything like it,'' she says. ''The whole film feels like one big action sequence and I see a lot of potential in revisiting this world.''

Theron's demanding work schedule is difficult to balance with motherhood. ''Yes, there's part of me that just wants to bond with [Jackson],'' she says. ''I have to be honest, there's another part of me that has been ignited and that's in my creativity.

''It's incredible. I look at this little thing and it makes me want to ask bigger questions and explore bigger things, so I'm lucky enough that I can pack him up and bring him with me. That's how I'm making it work.

''Like Morgan Freeman recently said to me, 'Life unfolds exactly how it's supposed to.' ''