Karen Armstrong, one of the world’s leading religious historians, found herself at the centre of an American media frenzy as she prepared to take up a scholarship at Harvard University last autumn.

For five months she faced endless TV and radio interviews, conferences and seminars, trying to inform the shocked American public about Islam and fundamentalism. Her book Islam: A Short History is a bestseller there - 8,000 copies were bought by the Egyptian embassy in Washington alone and sent to every US politician, including President Bush.

In January she joined experts on Afghanistan and terrorism at an educational retreat for US senators and congressmen in Mexico. She - and two Muslim scholars - were the first people ever to talk about religion to the United Nations’ assembly in New York.

In short, the former head of English at James Allen’s girls’ school in Dulwich, south London, is hot property on the other side of the Atlantic. Back home in London last week, as she was enjoying her relative anonymity, she found herself talking on a smaller stage - to pupils at Putney high school for girls.

But her message was the same: today’s young people will be responsible for making the world a safer place. To do so they will need accurate information about other faiths and cultures.

“We will be passing this mess on to the next generation,” said Ms Armstrong, 57. “They are the ones who will sort it out better than us because we are so stuck in our ways. But there must be no more chauvinistic teaching about Islam. Teachers have got to educate themselves about Islam - it’s our only hope.”

As The TES launches its appeal to help thousands of Afghan children and their teachers to get back to school, she said the same must go for children in Muslim countries.

“If all these children are being taught distorted things, then there is no hope for any of us,” she said. “We share the globe now and if you retreat from the world, like the Bush administration had been doing, then the world will come to you in terrible forms.

“What happens in Afghanistan or the Middle East today will be on our doorsteps tomorrow.”

Ms Armstrong’s own life has been steeped in religion. Born in Worcestershire in 1944, she was educated in Birmingham at the Convent of the Holy Child. She became a nun at 17 in 1962 and left after seven years.

“I was very sad to leave the convent. It was not a joyous thing, but I would have been a mediocre nun and it’s no good unless you are A1. At 17, you’ve no idea what forever is. I was far too young to make that decision and commitment.

“For all the harshness I would not have missed it. Youth is hard wherever you are. I learned a lot about myself and my limitations and that is always painful.

“What would I have been doing in the Sixties if I had not been in the Convent? Probably, strumming a guitar badly and singing ‘We Shall Overcome’.

Ms Armstrong read English Literature at Oxford University, gaining a BA and MLitt, before teaching for three years at London University and then James Allen’s girls’ school. She still teaches - part-time - at the Leo Baeck College for the Study of Judaism and the Training of Rabbis and Teachers in London.

In 1982 she became a full-time religious affairs writer and broadcaster. Her books have been translated into 37 languages. “I have seen it as a personal quest for myself as well as to flog a few copies,” she says. “It is a very absorbing discipline for me.”

Ms Armstrong now describes herself as a “freelance monotheist” who does not regard one religion as superior to another. “I’m fed by them all,” she said.

AN Wilson has described her as a “genius”, Anthony Burgess “a tough thinker”. Her best-known work, History of God, published in 1993, was a top-10 bestseller on both sides of the Atlantic but she feels she is appreciated more in America than in Britain.

“I sometimes feel like a prophet unrecognised in my own country,” she said. “Nobody is interested in me here. In America, I am seen as a scholar, while here, I’m seen as a kind of runaway nun.”