FOUR years ago she broke the record for the fastest solo circumnavigation of the globe. Now Dame Ellen MacArthur is giving up ocean racing to become an eco-warrior. She makes it clear this weekend that she will not attempt to regain the title she lost last year.

The sailor, who is 33 and 5ft 2in in wet socks, says she is so alarmed about the threat to Earth that she wants to concentrate on stopping mankind destroying the environment rather than embarking on new marine adventures.

She underwent an epiphany when she went to South Georgia in the south Atlantic and spent two months camping on the island to highlight the plight of the albatross, which is under threat from the hooks used in longline fishing.

MacArthur, who is the castaway on today’s Desert Island Discs on Radio 4, says: “After being on South Georgia, the more I researched, the more frightened I got. And that has scared me to the point where I can’t go back to sea and go round the world again because this really matters.”

When she set her record in 2005, she never slept for more than 20 minutes at a time because she had to stay alert to the hazards all around.

Her record of 71 days and 14 hours was broken last year by Francis Joyon, the French sailor, who took 14 days off the time. MacArthur had previously broken his earlier record by one day and eight hours, setting up their great rivalry.

She tells Kirsty Young, the radio programme’s host, that “there is a part of me that wants that record back, but something’s stopping me do it”.

The trip to South Georgia three years ago changed her attitude towards her life and her view of the world. “Down there for the first time I actually stopped,” she says. “I realised that on land we don’t see things as precious any more. We take what we want. And it started to make me think. I was looking at plans for the future and it hit home to me.

“This world, that I thought as a child was the biggest, most adventurous place you could imagine, is not that big. And there’s an awful lot of us on it. And we’re not managing the resources that we have as you would on a boat because we don’t have the impression that these resources are limited.”

MacArthur, who saved for her first dinghy by putting aside the change from her school dinner money, tells Young, “I didn’t think anything in my life could eclipse sailing”. But now she realises “how brutally selfish it is to go off sailing around the world, even when you are achieving your dream”.

Her new priority in life is sustainable living. Ironically, it was also looking back at her last voyage round the world which has made her think of what is precious and what we waste.

“When you sail on a boat you take with you the minimum of resources. You don’t waste anything. You don’t leave the light on; you don’t leave a computer screen on. And I realised that on land we take what we want.

“You’d never do that on a boat. If you need some kitchen roll, you tear off a corner, not a whole square. But someone somewhere thought that a perforated line was what everyone needs.”

MacArthur is putting her principles into practice by building a house on the Isle of Wight which she has designed on ecological grounds.

It has solar panels to heat the water. There is underfloor heating on the ground floor and a Rayburn stove plus two wood-burners. The house’s walls are 2ft thick with 8in of insulation.

She still sails, but just for pleasure and for her charity which helps children with cancer and leukaemia. “So will I invest four years again into sailing round the world? No. This new understanding has, for me, become far more important,” she says.

MacArthur, who was inspired to live a life of adventure by reading Arthur Ransome’s Swallows and Amazons books as a youngster, talks about her joy in buying that first boat with the £535 she had saved: “Suddenly this dream had become a reality. I remember going with mum and dad and seeing this tiny little blue boat and feeling so excited that dreams could happen.” She was somewhat stymied as she lived miles from the sea in the middle of Derbyshire, so her boat was in the back garden for most of the year while she simply sat inside it imagining a life on the waves.

“I then also realised that though I’d saved up for the boat, it cost money to put it on a reservoir. And I didn’t have that money. So I’d just have to make do with playing in the garden until the one week of every summer when we’d go sailing.”

Her book choice for the desert island is, as she herself “sadly” admits, the SAS Survival Handbook, while her favourite record is Don Henley’s The Boys of Summer.

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