Ahead of next week's State visit by the king and queen of Norway, the royal couple talk to Kathy Sheridan in their Oslo palace

The Vikings return next Monday morning and King Harald V of Norway knows that some delicacy is required. "Hopefully it will be with a bit more friendship and peace than we did the last time," he laughs. Given that the red-hair gene is reckoned to be of Viking origin, they left more than a few city ports behind them after the last big hove-to 1,200 years ago.

"It will be maybe a bit away from the coming of the Vikings. This boat is white," says the king, referring to the Norge, the royal yacht, that will waft the king and Queen Sonja from Dún Laoghaire up the Liffey, before dropping anchor at the North Wall at 11.15am for the start of a three-day State visit.

We are sitting in the queen's (literally) palatial office, on a stifling day in Oslo. The only signs of pomp and circumstance about the modest white palace, perched on open, public space on a hill overlooking the city's main thoroughfare, are the expressionless royal guard, who on some invisible signal, suddenly set off with remarkable precision for a quick march back and forth.

No high walls or fences separate the people from the working palace. Inside, the visitor is led by a pleasant, relaxed press secretary through splendid halls of grey painted floors, beautiful old rugs and magnificent chandeliers, the remarkable murals in the so-called "Bird Room", on to uncluttered offices, furnished with light, carefully-chosen antiques.

The queen, a commoner, who in another life says that she might have been "a teacher, or a sewing woman - I have a diploma from Switzerland - or interior designer maybe," is responsible for the decor. A startling feature of her office wall is an Andy Warhol original portrait of herself. "Yes," she says in precise, rather amused English, "I tried old-fashioned, elderly paintings in here but that didn't work." "I call them normal!" interjects the king.

Sonja, a connoisseur of contemporary art among other things, visited Warhol's New York factory in 1982, where, after some consultation, he smeared her with chalk "or something that made the whole face white", and took a lot of pictures. Warhol produced six portraits in different colours, one of which is in her office. Another hangs in the Norwegian National Gallery of contemporary art, and a third was bought back by the extended family at a New York auction.

HARALD AND SONJA are a team who seem to like one another. They have an easy rapport - she interrupts when she feels like it, he makes supportive asides, they seem to find a lot of things quite funny, and are formal without being stuffy. The monarchy is liked well enough by the people, although opinion polls suggest that their popularity is falling, especially with the young. Nonetheless, reports of royal events, weddings and christenings are a media staple in Norway. The last and only referendum held to determine if the country should have a monarchy was in 1905, but Harald's grandfather consolidated their standing when he stood up to Nazi (and some home-grown) demands to abdicate during the second World War and became a national symbol of resistance.

Through the generations they have melded into normal life. The king was sent to what he calls a "normal school" (although his sisters had a private school at home) and the couple then sent their children to regular schools where they had what the queen calls "normal friends".

Through the latest generations, they have weathered various storms, mainly triggered by marriage to commoners. The first was Harald to Sonja - "that caused quite a big fuss, yes," he says wryly. The second was the very controversial choice by Crown Prince Haakon of the glamorous Mette-Marit, a waitress and a bit of a wild child, whose history included a drug-taking boyfriend, with whom she had a son. But the ex-boyfriend never talked, the marriage went ahead and Norwegians took a "let's see how she behaves from here" attitude. Now at 33, she has supplied an heir, while becoming a hard-working royal and a crowd magnet on State visits abroad.

On living in the eye of the media, Harald comments: "I'm glad to say that - if you excuse my expression - it's not quite as bad as it is in Britain. It's a lot better, but it is developing in the same direction in a way. So we try to shield the small children from that sort of thing."

The queen nods in agreement. "We try to share - and ought to share - every event like weddings and christenings and birthdays, but there is a limit. We are particularly careful about the little space we have left, like when my husband is sailing and I'm walking in the mountains."

She will be 70 next year and is still walking mountains, although "a bit afraid of heights. I do it when I have the chance," she says.

"She's still young you know," insists her supportive husband. Her clear skin and slim figure are a testament to mountain walking.

She has been to Ireland a couple of times before, once in 1995 to open a "Viking Inspiration" jewellery exhibition in Dublin, when she also visited the Long Library in Trinity College. In 2002, she went on what she calls "a garden tour" from Dublin to Cork, and remembers particularly the Helen Dillon garden in Dublin and the one at Castletown Cox, Co Kilkenny, as well as a visit to Newgrange, to which she will not be returning, she says with interesting conviction. She recalls that although they took a helicopter to the Co Meath site, they returned by road, which left quite an impression.

"That road was bad," she stresses.

This time, she will be staying for four or five days after the State component, to take another gardening tour, with a particular eye on a return visit to Ballymaloe Cookery School in Co Cork.

Harald, the keen sailor, says laconically that he's just been around the Fastnet Rock, a couple of times. As the State visit includes a visit to Cork and a look at maritime operations there, he has been well briefed on sailing around Cork and its "oldest yacht club" status.

When she got married, Sonja recalls, she had to choose between sailing or golf. Knowing that she would have to spend much of her life listening to sailing talk from her father-in-law and husband, she decided that "if you can't beat them, join them . . . So I did sailing."

The king looks at her: "And she's very good at it. Yes."

Meanwhile, Harald, whose power is solely ceremonial beyond a veto that has never been deployed, describes the royals as "the glue of the nation".

His annual New Year's Eve address to the nation includes topics such as the environment and immigration, although he takes no credit for being a pioneer.

"We have ethnic minorities in this country and I think my father was the first to mention that now we have to look after them and make them feel at home in our country. We have a fairly large contingent of Pakistanis in this country, who came here in the 1960s and 1970 as economic immigrants. It can be an issue and of course now with everything going on in the world, people get frightened."

His take on the environment is long-term and practical. "We are a very sparsely populated country, a very large country with lots of space, and very few people. You can walk for hours without seeing anybody and this is something that is going to be a fantastic asset in the future. We still have space, moderately clean air and clean water - you can drink the water from the mountains."

Ask about Norway's fabled pro-woman approach at every level, and he is the one who notes that after the arrival of a baby, the father "has to take, has to take, three months of the year a couple is entitled to take between them. She doesn't get more than nine months - that brings her back into circulation while he is getting to know his baby."

The purpose of the forthcoming trip is to "strengthen bonds that are there already", he says. But the true purpose of course, is to do business. "Of course we have a big delegation with us and hope to do some business, attract some tourism, have some seminars . . ."

While we may expect to hear much about common bonds of our two countries - oppression, occupation, recent poverty, emigration - (until, crucially, they struck oil and we didn't) the king will only let it go so far. "It's not quite true about the poverty. For us, that stopped after the second World War. We were doing okay even without the oil. The oil has helped, my goodness yes, but we were doing all right through our shipping. We are a shipping nation."

We may also expect to hear something of Norway's many tourist attractions and Ryanair's new seven-day Oslo service from December, but much more about Norwegian energy in the coming weeks. Norway is the third-largest oil exporter and the eighth-largest oil producer in the world. Not many people know that. Only about 30 per cent of the estimated total resources on the Norwegian continental shelf have been produced. The country is looking around for customers and, according to one Norwegian official, cannot understand why Ireland seems to be looking towards Nigeria for supplies.

Ask the same pragmatic official about the state-owned Statoil's involvement in the Corrib debacle and the answer is?

"Do Irish people want gas or not?"

Norway fact file

• Population: around four and half million

• Has the sixth-largest surface area in Europe, with a 1,000 mile coastline, yet only six per cent are involved in farming, forestry and fishing.

• A US oil company once tried to buy its energy reserves for $100,000. Forty years on, petroleum is the country's largest industry, and the sector employs 80,000. Net cash flow from the sector stands at around €200 billion, which is ring-fenced for the Government Pension Fund. Nearly all its own energy consumption is from hydrogen.

• Norway has discovered a way of re-injecting CO2 under the seabed, which may be vital in resolving climate challenges.

• Norway has rejected EU membership in two referenda, but manages to be the Union's fifth-biggest net contributor.

• Famous Norwegians include playwright Henrik Ibsen, composer Edvard Grieg, painter Edvard Munch, writer Jostein Gaarder and explorer Roald Amundsen.