Yachtswoman Dame Ellen MacArthur announced her retirement from competitive sailing, to concentrate on environmental campaigning.
Appearing on Desert Island Discs on Radio 4, Dame Ellen, who broke the record for the fastest solo circumnavigation of the globe in 2005, said a trip to the Atlantic island of South Georgia had made her acutely aware of the challenges facing the planet.
At sea, every resource is precious and must be used carefully, she said - even something as commonplace as kitchen roll is eked out piece by piece - and this had given her a different view on the way mankind treats the environment.
"I never thought that anything in my life could eclipse sailing, I didn't think it was possible but after being in South Georgia, after learning these lessons I suppose, and the more I researched into it, the more frightened I got and that has really scared me to the point that I can't go back to sea and go around the world again because this really matters," she said.
She said she would continue to sail for pleasure and to raise money for good causes.
"I still sail, I love sailing, I'll still sail for pleasure, I sail for charity - the Ellen MacArthur Trust with kids with cancer, leukaemia, but as long as this challenge is there to be communicated, will I invest four years of my life to sailing round the world - no," she said.
"This new understanding for me has become far more important."
