Interview: Ellen MacArthur - Voyage of self-discovery

• Dame Ellen MacArthur at Portree on Skye

IT WAS one of those profoundly moving, revelatory moments that has made the TV series Who Do You Think You Are? such compelling viewing. But there were no film cameras around when Ellen MacArthur and her father, Ken, solved a family mystery that had been puzzling them for years.

"Dad and I were sitting in Portree Library looking up archives, hoping to find out more about the history of the MacArthurs," she says, recalling her first visit to the Isle of Skye in 2001, after she competed in the Vende Globe, the single-handed race considered to be the ultimate endurance test in sailing and in which she came second but found worldwide fame.

Fresh-faced, with a direct grey-blue gaze and dark brown hair cropped into an elfin cut, she explains: "I'd never been to Skye before. If we hadn't all loved sailing after my aunt got a boat, all our summer holidays would have been spent there because mum and dad and my two brothers love Scotland."

Poring over ancient documents on microfilm, father and daughter discovered, from the 19th century censuses that they are descended from a long line of herring fishermen on Skye. "My dad's great-grandfather – Donald, I think – moved south during the Highland Clearances, to Derbyshire and a little village called Belper.

"And, yes, it really was one of those Who Do You Think You Are? scenarios, although it was years before they did the TV programmes," says the fast-sailing, fast-talking 34-year-old who was to become the world's greatest sailor.

"I had grown up on a smallholding in landlocked Derbyshire and no-one could understand how someone from a family of landlubbers had such an innate love of the sea and sailing. I've told the story many times of how, ever since the age of four, I'd dreamt of being at sea.

"Sailing Cabaret, my Auntie Thea's boat at Burnham-on-Crouch, was my first experience. From the age of eight, every penny I could save, including my school dinner money, went into buying my own boat. I dreamt about the sea throughout my childhood; I wanted it so much.

"So it was amazing to find that I really did have the sea in my blood – salt water in my veins! I'll never forget the emotion I felt when I learnt that I actually came from a seafaring family; it explained everything, including why I feel so incredibly at home there."

She recalls laying on the back seat of the car as her teacher parents – her mother Avril's family, the Lewises, moved from Edinburgh to England two generations ago – drove around Skye. "I was exhausted after the Vende!" she exclaims, but she also remembers thinking, "I came from this; this is part of me."

In Full Circle, the latest volume of autobiography – her third and most reflective – MacArthur writes: "I remember the bright-green slopes and sheep up on the hills, and the feeling of contentment that I had there. Things could have turned out very differently in life, and I honestly believe, looking back, that if Mac (her beloved Border Collie cross] had had the herding instinct in her, the girl who spent her weekends at farm-sales with her Dad would have probably become a shepherd."

Of course, MacArthur – who was made a Dame after breaking the solo non-stop, round-the-world record in her trimaran B&Q in 2005 – did not take to the hills. However, she did lose her heart to Scotland on that initial trip.

Now, she has a holiday home on Skye, to which she and her partner, Ian McKay, return often from the Isle of Wight, where they have recently built a house – "designed on ecological principles, complete with solar panels to heat water, a Rayburn and two woodburners" – on a plot of land MacArthur bought a while ago, and where they also grow their own vegetables and lavish affection on their two dogs.

She also owns a piece of land on Skye. One day, she says, they hope to get around to building a similar thick-walled house there – again, doing much of the hard graft themselves as they've done on the Isle of Wight.

A wee home from home for the family she may have one day?

"That's not on the schedule at the moment," she replies, although when I ask her if she would allow her daughter, if she has one, to sail off on her own around the world, she says that she hopes she'd give her child the sort of freedom her parents gave her. "They let me follow my dreams. Sometimes I don't know how they let me go off alone knowing that some sailors had not returned from these races. They must have been scared stiff. They were so brave."

For the time being, though, the 5ft 2in but formidable MacArthur is channelling her whirlwind energy and considerable charisma into her latest project after announcing in 2008 that her ocean-racing days are over and that she will no longer pit herself against the elements.

Today (September 2] she launches the Ellen MacArthur Foundation, a charity for which 6 million in funding for the next three years has already been raised from donors in business and industry. She will run it in tandem with the charitable Trust, which she started in 2003, and which takes youngsters with cancer and leukaemia sailing.

Her passionate belief in the Foundation, as she recounts in Full Circle, began with a trip to South Georgia, where she viewed rusting whaling stations and saw how long-line fishing is depleting the albatross population. It opened her eyes to the fragility of the future of the planet's resources and now she plans to devote herself to campaigning for a more sustainable future.

When you sail you get a sense of how vast the oceans are, she says, sipping a cup of tea. "You feel so insignificant on them. However, it also gives you an idea of the size of the planet and if you can sail around it in 71 days, it's not that big. But you do realise there're only so many resources. These are lessons we should have learnt, yet we haven't."

In her book, she writes of her decision to stop sailing competitively: "Perhaps it's like loving someone so much but knowing you simply can't live with them any more." Nonetheless, she's still going down to the sea and sailing with the kids from her Trust.

"I'll never stop sailing for fun, of course, but I've no regrets having made the decision to turn my back on the sea," she says, then adds that she wants to get one thing clear. She's not – as certain newspaper headlines have reported – "giving up the ocean to save the planet". It's all about resources and the fact that they are diminishing all the time.

"I'm a realist. I want to help to do something about it because this really matters. I'm not an eco-warrior. I am not talking about man's destruction of the environment. It's about sustainability and I'm devoting my life to it.

"We're launching the Foundation, with a very small team, after four years of intensive research and 18 months of work, planning how to link education and business. The message is being taken into schools, because we have to prepare the next generation for the fact that our resources are finite.

"It's a huge challenge. We have to design a way of not using things up, to stop our 'take, make and dispose' economy."

As for the future of the planet, MacArthur says that it was her first solo voyage around Britain, on the Iduna when she was 18, that changed her life – and it's those memories of that adventure that make her determined to pass her love of the sea on to other youngsters, especially through her Trust.

"On that journey, I grew in confidence. I met new people and I discovered so much beauty. Seeing my first wild dolphins in crystal-blue water as I sailed out of the tiny harbour of Stonehaven is still one of the most exciting moments of my young life."

Despite the fact that she knows that her Foundation will take over her life just as racing the seven seas once did, she says: "There's a piece in the jigsaw that, for my heart and soul, I could never remove. That isn't only sailing, but the best sailing I could ever imagine: with the incredible, inspirational young people with cancer. Their joy and enthusiasm for life is so humbling. They're always laughing and joking. That's true courage."

She pauses and says: "I suppose that's why I still crave normality, why I'm determined to find the energy to stay being me, to stay who I am. It's so precious to know what you stand for, what your history is, who your family is. It's not who do you think you are, but who do you know you are?"

• Full Circle: My Life and Journey by Ellen MacArthur is published by Michael Joseph, priced 20.