Wangari Maathai - who this week became the first environmental activist to win the Nobel Peace Prize - was sunk in a rare moment of depression. It was in early 1992: we were speaking during a few days between her coming out of hospital, after being mistreated in jail, and yet another appearance in the dock.
"I am certain," she told me, "that I was not born to spend my entire life at the front line, fighting battles which never seem to end." But then she rallied: "We know we are going to have to pay a price for what we hope will be a more just society. It is very painful, but I realise somebody has to pay a price." She was all too prophetic. Just days later, already in her 50s, she was back in hospital, clubbed senseless by police.
Wangari Maathai, who is the first African woman ever to win any Nobel prize, grew up in Nyeri, central Kenya. She remembers drawing water from a spring, "fascinated by the way the clean, cool water pushed its way through the soft red clay so gently that even the individual grains of the soil were left undisturbed". The area was so green that there was no word in the local language for desert.
Now the trees have been cut for tea plantations and Wangari's spring has dried up. "I feel the tragedy under my feet. Gulleys stare at me, telling the story of soil erosion, unknown before. Hunger is on the faces of the people." It is like that all over Kenya - and Africa. Just 2 per cent of the country's original tree cover remains. Four-fifths of the continent's productive land threatens to turn to desert.
For more than 25 years Wangari has worked to reverse this, founding and running the Green Belt Move- ment, a grassroots campaign mainly of poor women, which has planted some 20 million trees. After becoming the first woman PhD and university professor in East and Central Africa, she married a rising politician, who got elected after pledging to plant trees in a slum area. She fulfilled his promise, to the fury of politicians who feared she was setting a dangerous precedent.
Three years later she started her movement, but before long her husband divorced her for being "too educated, too strong, too successful, too stubborn and too hard to control". She was regularly denounced by the country's leaders for not being a traditionally docile Kenyan woman.
She retorted that she was "sick and tired of men who are so incompetent that every time they feel the heat because women are challenging them, they have to check their genitals to reassure themselves".
Frequently assaulted and imprisoned for her campaigns, she helped lead political opposition to President Moi. In the early 1990s I nominated her for a Goldman Environmental Prize - the world's top prize for grassroots environmentalists - which she won. She told a BBC World documentary this year that it had provided a "protective shield".
Two years ago, when President Moi was defeated, she was elected to parliament for Nyeri with 97 per cent of the vote, and was made Deputy Minister of the Environment. "I don't really know why I care so much," she says. "I just have something inside me that tells me that there is a problem and I have got to do something about it. I think that is what I would call the God in me. It must be this voice that is telling me to do something, and I am sure it is the same voice that is speaking to everybody on this planet."