At just 32, Charlize Theron has an Oscar on her mantelpiece and is once again ditching the fair locks to play a dogged detective in Crash director Paul Haggis's upmarket drama In The Valley Of Elah.

"It is the best thing that cigarettes have ever given me," laughs the South-African born actress, who met Haggis when the pair nipped out for sneaky fags while stomping the awards beat (she had been nominated for North Country). "We were the only two sad cases outside in the alley."

He promised to write something for the star and came up with In The Valley Of Elah, a biting anti-war movie that sees Tommy Lee Jones searching for his Awol soldier son who is just back from Iraq. Charlize is the world-weary single mum cop who helps him.

"I want to be in films which ask questions and deal with social issues," she admits. "I never really go for glamour roles. I like roles which make you think about the character and their life, rather than what they look like."

Looks have always played a part in Charlize's career, first as a catalyst for her initial success and then as a crutch when she wanted to try doing more serious parts. There was more commentary about the fact she 'uglied up' for her Academy Award-winning performance in Monster than her actual acting.

"It's a shame, because I love glamour," she says, hinting at everyone's obsession with outer appearance and belief that beauty is skin-deep. "I grew up on Fred Astaire and Ginger Rogers movies and when you look at these films, the women had beautiful dresses and gorgeous make-up. Women were much more celebrated on screen than they are now. They were allowed to look beautiful but still have depth."

Nonetheless, Charlize says that she's never experienced the kind of blatant sexism her character Emily suffers in In The Valley Of Elah. "But I know plenty of women who do, in all sorts of circumstances," she says. " The guys always think they are joking, but for us women, it is offensive and intimidating."

The iniquities of Hollywood may be why she has only just returned from a two-year hiatus, spent, she says, "catching up on life" with Irish actor boyfriend Stuart Townsend. "I wanted a break and to enjoy time with people who matter in my life, like Stuart and my mum, Gerda," she explains.

"We also travelled a lot - Greece, Turkey, Belize and Guatemala. We went back home - to South Africa, in my case, and Ireland, in Stuart's. It gives us a great feeling of joy to throw on a backpack and live the culture for a month, staying in places which are not five-star hotels."

She didn't, however, use the time to clear up the rumours and get officially hitched to Townsend. " We are married in our own eyes," she says. "We are not married by church and state and did not go to a service, in the eyes of God. I did not wear a white dress. But, as far as I am concerned, we are married and I have a ring. I think it is an old Victorian ring."

It's a remarkable turnaround for a girl whose childhood began as someone who " had a very active imagination and loved putting on make-up, costumes and playing characters".

Then, as she confesses herself, " everything changed" thanks to the horrific incident of witnessing her mother shoot and kill her abusive father. In early interviews, she said he died in a car crash before unveiling the truth. But she believes being honest about the past has only made her stronger.

"It made me realise that life deals you some really nasty cards and you just have to play them," she says, simply.

"I can remember thinking, 'I want other cards than these'. I walked away from that experience knowing that I had two clear choices - I either drowned or started swimming, very fast.

"I refused to sulk and feel sorry for myself," she continues. "I made the decision to move on and realised that certain things in life were not meant to be.

"I could not be stuck and allow myself to be defined as a person by that one event."

A chance meeting with a model scout when she was 16 led to a career on the catwalk and when a knee injury put an end to her dream of becoming a dancer, a fluke encounter thanks to an intractable Los Angeles bank employee did the rest.

"My mother had sent me a cheque to help pay my rent and I was trying to cash it in a bank on Hollywood Boulevard," she recalls. "A clerk refused - and I just went nuts. After the shouting was over, a man handed me his business card and told me to get in touch. He turned out to be a genuine talent manager and he introduced me to some casting agents."

So despite an inauspicious start, Charlize now finds herself at the top of the Tinseltown tree. She will star opposite Will Smith later this year in superhero comedy Hancock and is rumoured to be reprising her role in a sequel to The Italian Job. What's more her beloved Mum has now remarried - " to Doug, who is in insurance" - and is happy and Charlize, herself, " is with a wonderful man, living a dream".

Quite frankly, she grins, "if I complained about anything right now, it would be obnoxious" .

In The Valley Of Elah is scheduled for UK release on January 25.

Factfile

Age: 32

Name: Charlize Theron

Significant other: She says she is married to Irish actor boyfriend Stuart Townsend, though they've not officially said 'I do'

Career high: Her Oscar-winning turn as serial killer Aileen Wuornos in Monster

Career low: The first film she made after winning, the truly dreadful Aeon Flux

Famous for: Being the first South African to win an Oscar - and then showing it off to Nelson Mandela

Words of wisdom: "I'm 50-50 on glamour stuff. I'd rather put on a pair of jeans and get on my Harley and act like a guy."