“Very sorry but the PM is running about half an hour late. She’s seeing the Queen. Please sit tight.” That’s not the sort of text message I usually get at 3pm on a Friday. And I don’t mind in the least sitting tight in the elegant surroundings of London’s Sofitel St James hotel, on the corner of Pall Mall, waiting for Helen Clark, the prime minister of New Zealand.

The hotel’s Rose Lounge couldn’t really be called anything else. It is a vision of pink and green, with chintz upholstery and twee lampshades. It is rather like the sitting room of a prim aunt.

I look wistfully at the silver cake-stands being delivered to the other tables, each tier promising tuille biscuits, dainty cakes and finger sandwiches. I hope Clark hasn’t filled up on Battenberg cake with the Queen. Thirty minutes pass. I reach for a book from the shelf - Tiaras: A History of Splendour. That couldn’t be less appropriate for the down-to-earth, straight-talking leader of the furthest nation of the Commonwealth. I quickly put it back in case she catches me.

Forty-five minutes pass. A man who pronounces Bev as “Biv” approaches and shakes my hand. He is Clark’s press secretary and assures me the PM isn’t far away - she’s just freshening up in her room. And finally, a few minutes later, a tall, athletic figure walks confidently past the tables of ladies who take tea and businessmen who are talking golf, without a blink of recognition from any of them.

Dressed in a tailored black suit and black boots, Helen Clark smiles, apologises for the delay, and makes herself comfortable in the rather upright chairs. Despite the newly applied make-up she looks tired, which is perfectly understandable for someone who flew across the world the day before and doesn’t appear to have stopped since. But she is too professional to flag - she gives me another encouraging smile and scans the afternoon tea menu. “Orange-blossom tea - that sounds good.” Tea? Just tea? Can’t I tempt you to some sandwiches or cake? “No, no thank you. A pot of tea will be fine.” We order orange-blossom tea for two, and I silently curse the caterers at Buckingham Palace.

Although Clark’s face isn’t familiar to the other guests in the Rose Lounge, her deep and measured voice may well be. In the run-up to the invasion of Iraq in 2003 she seemed to be regarded by Radio 4’s programme producers as the political voice of reason. New Zealand - unlike its closest neighbour and ally, Australia - did not join the war in Iraq. Clark said she felt that the case for war had not been made - she wanted a UN security council resolution as a basic condition.

She strongly advocates an independent foreign policy for New Zealand, placing her Labour government a long way from the traditional New Zealand position of total loyalty to the motherland. At the start of the second world war, the then prime minister Michael Savage declared of England: “Where she goes, we go. Where she stands, we stand.”

Clark, who is 56, says the greatest influence on her in terms of war was being part of the Vietnam generation and knowing that it was wrong. “You have to be very careful about decisions where you commit other people’s children to go and fight a war. Vietnam was not a just cause. And nor was Iraq. They are value judgments, but they happen to be my values.”

Yet Clark has been a driving force behind the unveiling of the New Zealand memorial at Hyde Park Corner, to commemorate those who died fighting for their country. “There’s been a lot of unfinished business for New Zealand soldiers - traditionally they came home from war and everybody shut the door on it, they never talked about it again. But I have a great interest in heritage and I think you have to properly commemorate significant events in a country’s history.”

She describes the memorial - 16 slanting bronze “standards” in formation that could be troops on parade, or Maori performing a haka, or a cricketer leaning forward to play a defensive stroke - as a work of art: “It is a beautiful and creative design. The patterns on each standard are highly symbolic of the people who make up New Zealand, the literature, the birds, the shoreline, the forest. It’s a statement about New Zealand today.”

When Clark became prime minister in 1999 she also took on the portfolio of minister of arts, culture and heritage. She believes these are the areas that forge New Zealand’s identity and can help it get noticed on the world stage. “We are a country of four million people. We are geographically remote, so we have to find ways of saying ‘Look at me’ as a country.” Not a natural show-off, she laughs, almost apologetically. But this philosophy is one of the reasons her government has increased funding to creative industries such as film. “Film is an iconic industry and if your country is producing great movies then that has a cachet about it. The Lord of the Rings has given New Zealand fantastic publicity in the past seven or eight years, and it was followed by King Kong and The Chronicles of Narnia, also made by New Zealanders.

“The other way to get international attention is to host very large events, such as the America’s Cup, and then leverage off that. We’re now looked on as world-leading yacht designers, and builders of super yachts and marine technology. The film industry also enables you to showcase your technology and digital solutions, so New Zealand becomes a place where you’d be interested in buying very sophisticated goods. In other words, we’re trying to shake that chocolate- box image of 1950s sheep and mountains.”

By now our tea has been poured from the inevitably rose-speckled teapot into our china cups. I am reminded of David Lange, a previous Labour prime minister, who in 1988 famously announced it was time for the country to have “a cup of tea”, meaning a pause in the free-market frenzy of reforms unleashed by his finance minister, Roger Douglas. At that stage Clark had been housing minister, struggling to keep state houses (provided at affordable rents for people on low incomes) from being sold off or rented out at market rates. Now, as prime minister, she is able to introduce a range of left-leaning policies, with social justice at its core. “I had to bring our Labour party back from the lurch to the right.” She says her administration is more consistent with the first Labour government, elected in 1935 and renowned for creating the country’s welfare state and providing free healthcare and a universal pension.

However, some ideas pioneered in New Zealand in the 1980s have migrated to the UK - such as giving the Bank of England the independence to set interest rates and so keep inflation under control. And the country continues to be a social laboratory for Britain. The call by the Conservative leader David Cameron for a points-based system to ensure immigrants have the skills the country needs mirrors the New Zealand experience. And Tony Blair’s government has been studying the KiwiSaver scheme where employees receive NZ$1,000 (₤345) from the government if they start saving regularly to top up their state-provided pension.

One idea the UK has not adopted is proportional representation, yet Clark is proving adept at leading a coalition government after winning her third term in office in September 2005. “On 41 per cent of the vote [Labour] have a minority of seats. So we govern through relationships and understandings with other parties, and that requires a particular style. You can’t be an autocratic ‘it’s got to be done my way or the highway’ kind of leader, because people won’t deal with you.”

She says that being a woman, and having women in senior positions in her government, suits this system. “I think the style I’ve developed -that you’ve got to work things through with people, try to get a result everyone can live with - is very appropriate for this style of politics.”

Perhaps Clark is mellowing after seven years in the top job: in the past she has been described (by friends, colleagues and the media) as a control freak, “the minister for everything”. She does admit to being self-sufficient, something that comes from her upbringing as the oldest of four daughters on an isolated North Island farm. “The way I grew up means that I’m very self-contained. And you need that to operate in politics. If you allowed yourself to feel every sling and insult and bit of unpleasantness you’d be a nervous wreck.”

And there were other benefits to her early family life: “Because there were no brothers, the girls got to do the things the boys would have done on the farm. So it’s probably quite emancipating not having brothers. I got to drive the tractor,” she chuckles.

Is there a mood in New Zealand to be similarly emancipated from the monarchy? Clark almost sighs - I suspect she is asked this question by every journalist she meets in Britain. “Nothing’s going to change fast,” she says. “My view’s always been that the relationship between New Zealand and the monarchy will change, but it will be another generation away. The family link with Britain for most people is, say for my generation, more likely to be a grandparent than a parent. For my nieces’ generation it will be a great-grandparent, so the links start to attenuate a bit - most New Zealanders now are pretty firmly rooted in their country. Over time I think people will say, ‘Well, isn’t it time that somebody like our governor-general was the head of state?’”

As for her own future, she has every intention of contesting the next election, for her fourth term. Retirement is not on the agenda, but it holds no fears. “I’ve got plenty of skiing I’d like to do, trekking I’d like to do, books I’d like to read, plays I’d like to go to.” These are interests she shares with her husband, Peter Davis, who is professor of sociology at Auckland University.

My tea has gone cold, but at least Clark finished her cup. She stands up, shakes my hand and heads upstairs to her room - she reckons she’s got time for some sleep before her evening schedule kicks off.

The Rose Lounge, Sofitel St James London SW1

1 x pot orange-blossom tea

Total: ₤10.13