Dame Silvia Cartwright sits in an armchair at Government House, Epsom, cut-crystal glass at her elbow, public affairs officer standing at attention, central heating purring like a contented cat. The outgoing Governor-General who represents the Queen in New Zealand is perfectly at home.

Not a silver hair is out of place. She chooses her words carefully, speaking with the rounded vowels she grew up with, which sound so posh in multicultural Auckland. The black pants and top are snug and simple, the beige jacket elegant. Her blue-grey brooch adds a touch of colour, the taper-toed shoes a hint of glamour. Dame Silvia herself adds the sense of majesty.

Next month, when she arrives in Phnom Penh, the Governor-General will be plain Justice Cartwright again. But even on the Cambodian War Crimes Tribunal, where she will sit in judgment on a line-up of some of the most atrocious mass murderers in modern history, you can be sure she will exude that majestic presence.

At nearly 63, after a near-blameless record, hundreds of speeches and interviews, Cartwright admits her bulletproof poise may be hiding "a bit of natural fear and tension".

Now the end of the job is in sight she peppers her conversation with smiles and the occasional giggle. Her blue eyes glisten like a girl's when she talks about her family, friends and parents.

Those who know her say she makes wonderful friends and sustains them, and you can measure that by her loyalty to those who are part of her past lives. Louise Callan, her researcher-writer during the Cartwright Inquiry of 1987; Alison Henry, whom she met at Harkness Henry law in Hamilton in the 60s; Brent Scott, her associate at the Auckland High Court; and former TV star and life-long friend Catherine Saunders.

All get regular phone calls, emails and help when they need it. And they have all been invited to her farewell party for around 100 at Government House Wellington, tonight.

Henry talks about "Sil's" beloved Boston terriers, Thelma and Louise, her two-day "fishing trip" at Government House for the bunch of women who take an annual five-day trip out of Whitianga.

"Because she was G-G Sil hadn't made it for five years, so she had one there," says Henry. "I remember the table centrepiece was four goldfish in a vase - and she paid for it out of her allowance."

Saunders remembers how Cartwright and her husband Peter, flew, breakneck, from one side of the world to the other to spend an hour with her mother before she died. "To a lot of people it wouldn't have mattered [to arrive before the death]. But to Silvia it did."

It is her way with people, coupled with her drive and presence, that differentiates Cartwright's period as Governor-General. While her predecessor, Sir Michael Hardie Boys led one international state visit, Cartwright has headed 15. She ticks them off on her pink-polished, fingers. "Southeast Asia, the Gulf States, Europe, Latin America - everywhere but Africa."

This is new territory for our Governor-General, who as Head of State, is bound to avoid matters political. But, as Cartwright explains, a figurehead job would not have been as fulfilling and she believes her state visits have smoothed the way for new and better relationships.

"The point is there's only one person in the country who can open the doors that I open," she says. "I can't open the doors the Prime Minister can open, but I can go and meet my equivalent at head-of-state level, which gives a burst of publicity about New Zealand in that country.

"They literally close the city while you drive through. There are New Zealand flags everywhere, big ceremonial welcomes with reporters, news photographers and it's New Zealand's day in the sun. It's not focused on me, it's focused on the relationship. No one else can get that particular bit of publicity - and we have to use everything we've got."

Cartwright's strategy for her state visits was three-pronged. Armed with Foreign Affairs briefing papers, she "learned the country" then swotted up on their desired outcome from the visit.

"Often there are military connections," she says, referring to Crete, Korea and Turkey where people still remember New Zealand soldiers with tears in their eyes. "It's like walking into a big family gathering, which sometimes goes back nearly 100 years in battle."

Now, she says, the trick is to make sure that warm, intense relationship, which is often helped along by inter-marriage, moves on to next generations. In Vietnam, although we were there in a military role, we did support work and aid, and we're greatly loved for that.

The second part of the strategy was using her high-voltage charm. As Cartwright says, "A lot rides on the personalities. If you don't establish a rapport with the head of state you're visiting then they'll think 'boring lot' or whatever and move on."

Did Cartwright's visits achieve the desired results? Her Chile trip coincided with the announcement of a trade agreement between Chile, Singapore, Brunei and New Zealand.

In Vietnam she met the "charismatic" secretary general of the Communist Party, opened Victoria University's campus in Ho Chi Minh City and played a part in securing an agreement on tariffs and access for New Zealand goods.

While her visit signalled that New Zealand was serious about advancing its free trade agenda with Korea, Cartwright worked on establishing a rapport with President Roh.

Much of her energy has gone into Britain where, "in a different sense, the relationship is also in danger". Why? Because of New Zealanders becoming complacent about the ties between the two countries, and new generations of Britons "not quite understanding why we are friendly".

She says the English do not share the same intense feelings for New Zealand as the people of Crete, and despite the many talented New Zealanders living there, "It's a different friendship now."

"So we need to form new reasons for that friendship. This is especially important from New Zealand's point-of-view because trade and those sorts of relationships are crucial to our survival as a nation."

As she explains, after the abrupt severing of New Zealand butter's access to the European Union, "now all depends on the good connections that ministers and trade people have made to get it back on track as soon as possible - without waiting for some arcane court system."

She will not be drawn about New Zealand becoming a republic: "I have no views on the subject, I'm the Queen's representative in New Zealand." She suggests, "We often overlook the intense loyalty and love the Maori people have for the Queen - probably more intense than many people of European descent. This is a history that's never going to die."

So, after all that, why the Cambodian War Crimes Tribunal? Partly because Cartwright was "not overwhelmed with glamorous offers", partly because she's "an internationalist at heart", mostly because it's "right up my alley".

"I was a judge," she says. "This is where I feel I can make a realistic contribution."

What she doesn't mention is the sense of duty handed down by her hard-working Baptist parents. Her mother became a school librarian in her mid-50s and stayed until her mid-70s. Cartwright routinely starts her day at 6am-7am with breakfast meetings and finishes around 11pm.

She is also conscious of her role as a female trail blazer in the legal world - and the importance of having a woman on the Cambodian tribunal.

Certainly, the United Nations committee thought highly of her pedigree. Cartwright and three others were selected from a shortlist of 11 international judges. Only she and the French judge will sit on the bench.

"Two of the others are assigned to appeals, should there be any, and the rest are in reserve - presumably in case I drop dead!" she says with a lift of the eyebrow.

It will be chilling stuff. More than a million civilians were killed during the genocide and "forces" still operating beneath the radar have kept the trials at bay for 30 years.

Cartwright guesses the tribunal will sit for between two and four years and try a selection of the most senior of the Pol Pot regime, rather than "everyone rounded up".

Already, the judges, from Poland, Sri Lanka, US and France are sworn in and waiting in Cambodia. Cartwright is conscious she started "learning" the country only last week.

After this trip it will probably take a year of evidence-gathering before proper proceedings begin, which will give her time to "swot up" her French (all judges must speak either Khmer or French) to make the required standard.

Cambodia will be challenging practically, too. The tribunal is based an hour's drive from Phnom Penh with its rudimentary infrastructure.

"I did wake up in middle of the night ... thinking 'the cockroaches are going to be huge'."

But, laughs Cartwright, her arms are "polka dotted" from the vaccinations of five years of world travel.

Her husband Peter, also a lawyer and former chair of the Broadcasting Standards Authority and ACC Appeal Authority, will go along for the adventure.

It is a long way from Cartwright's childhood as the third daughter of Eileen and Monteith Poulter who ran a small knitwear business in Dunedin. The six children claimed Scottish ancestry from their mother's McBay clan and spent much of their time at the Hanover Street Baptist Church.

For her parents, who both had to leave school early, education was the key to success. "My mother, who was in line for dux, had to leave school two months before the end of her last term," says Cartwright. "She was offered a job and my grandfather was out of work and it was the Great Depression and she had to support the family."

Cartwright's younger sister, Adrienne Poulter, now a needs assessor for the elderly at Auckland Hospital, remembers "they were wonderful parents, very liberal. Father was a very strong feminist and we adored each other as siblings. We were certainly not deprived."

Cartwright, probably the most ambitious, decided early to be a lawyer. She won a bursary to Otago University and had a holiday job in an apricot factory, then moved on to the musty law practices of the early 70s.

Women were an oddity, but Cartwright's rise was sensational. She became a partner in the Hamilton law firm, Harkness Henry in 1971, a District Court judge in 1981, and, six years later, headed the inquiry into cervical cancer treatment at National Women's Hospital.

The inquiry led to Cartwright's fame, her damehood, and her only slip-up: when she was photographed celebrating with feminists Sandra Coney and Phillida Bunkle, who had raised the alarm.

Despite a few tut-tuts, the slip didn't harm Cartwright's career. Two years later she became the first woman Chief District Court Judge and, in 1992, was elected to the UN's committee on the elimination of discrimination against women.

A year later she was made New Zealand's first High Court Judge and eight years after that, in April 2001, she stepped up to Governor-General.

But as Cartwright has said, men's attitudes prevented the majority of women from following her lead.

"It is my fear that women's foothold [in law] may turn out to be tenuous," she told the Herald in 1993. "We do not seem to be consolidating the inroads we have made ... there is a deep sense within me that says 'of what advantage is it to women to join this profession unless its essentially male nature and attitudes can be transformed?' "

She is still not convinced that the workplace has changed enough. "Women should be able to have the best, most exciting, careers as well as having children," she continues. "It's a conundrum because I want them to have both if that's what they want.

"But I look at some of them and the lives they lead and it's very, very, difficult.

"They don't realise how fragile the gains are and how easily they slither away. And one day they'll wake up and say, 'Oh my God, we've got to start all over again'."

The other thing she wanted to work on was the appalling rate of child abuse. Five-and-a-half years later she admits defeat. As Governor-General, she had little opportunity either to speak out against abuse or do anything about it.

"If I feel I've succeeded in changing anything, no, I don't," she says sadly.

"I've never been able to understand how people can abuse their own children physically and sexually. What happens to a human being to be able to behave that way?"

She tells of a man who came before her in court, arguing that he didn't sexually abuse his 8-year-old daughter, but that she was a naughty girl and told on him out of vengeance because he'd always physically disciplined her.

"He took off his belt with this big buckle and said, 'My Dad used to hit me with a belt like this and it never did me any harm'.

"The irony of it! Here he was in the dock on very, very serious criminal charges, saying, 'It didn't do me any harm'."

Cartwright is childless by choice. "In the days when I was a lawyer I would have had to give up work if I had children. It was all or nothing and I liked what I was doing so I kept doing it.

"You didn't tell anyone in those days. We just let them think ... " her voice trails off almost to a whisper, "we couldn't ... really."

And then, in typical Cartwright style, she breaks the mood.

"Are you going to get cross with me?" she asks her minder, Stefan Wolf.

"He's terrified I'm going to blow my last interview!"