The answer is that she used to carry out female circumcisions, and he has pioneered a new technique to put right the lasting damage done.
What a subject to be discussing over tea and scones in a neat, north London sitting-room. My host, Harry Gordon, a consultant gynaecological surgeon, is telling me about reconstructive surgery for women who have been "circumcised", a technique which he has pioneered at the Northwick Park Hospital. I have not been looking forward to seeing his slides, but to my surprise I find them quite heartening - if only because Harry Gordon has made an extraordinary discovery.

"You can see the leathery scar tissue, on the outside," he says, showing me "before" and "after" pictures. "But underneath, when we cut through the scar tissue, there is the clitoris. Sometimes it just pops up and looks at you. So it's not true - as we'd been led to believe - that everything has been scraped away."

Harry Gordon thinks that circumcisors in Somalia - home to most of the 200 women he has "repaired" - have been doing a kind of cover-up job, knowing that the risk of a girl bleeding to death is high when her clitoris is cut because a major artery runs through it. "What's happened in 95 per cent of cases is that a bit of labia was cut off on the outside and then the sides put together [infibulation]," he says. "Our aim is to restore women to 100 per cent normality by repairing the outer labia with very fine catgut. After a week or two, everything heals and the reversal is complete."

Harry Gordon is a courteous, grandfatherly figure under whose auspices the African Well Woman Clinic was set up at Northwick Park in 1993. "The clinic is a very cheerful occasion," he says. "The women come dressed up and stay all day, sometimes bringing stoves and brewing tea on the lawn with their friends. They won't volunteer information about themselves, but if you ask 'Are you closed?' they say 'Yes'."

Young husbands have often turned up at reception, communicating by means of hand signals that sexual penetration of a "closed" wife is virtually impossible. Yet many of the women he sees are pregnant, despite having a vaginal opening of only one centimetre. ("One husband told me they have anal intercourse and then ejaculate near the orifice," says Harry Gordon). He aims to do the reversal operation well before women go into labour, using a spinal anaesthetic. "Many ask to be resutured after delivery because this is part of their culture, but it is illegal here. My refusal is always greeted with a beautiful smile."

"Female circumcision" or "female genital mutilation" is widespread across the broad belt of countries from the Horn of Africa in the East to Mali in the West, and with the huge influx of refugees to Europe from this part of the world in the past five years, Harry Gordon believes there are many thousands more women in this country who could benefit from treatment - or at least from a greater understanding of the issue. "Increasingly, midwives, nurses and GPs are treating circumcised and infibulated African women in major hospitals, not knowing what they are seeing. There is total ignorance, and the general attitude of British gynaecologists is polite disinterest."

Yet the death toll from this procedure is estimated to be 10 per cent in the short term (from haemorrhage, shock and infection). Another 25 per cent of women die in the long term from recurrent urinary and vaginal infections, and complications during childbirth (such as severe bleeding and obstructed labour). Pain during intercourse and infertility are also common problems, while the impact on a woman's psyche can't be measured.

An estimated 10,000 girls of African descent now living in the UK may yet endure the procedure. "We think there may be a few rogue nurses doing this in the UK, but there is a web of silence around the issue and they have been impossible to catch," says Harry Gordon. "There was a flourishing trade in Paris until last year, when three girls died and their families were prosecuted."

But mostly, it happens when children are taken back to Africa. "A child may be told that something special is going to happen when she goes on holiday," says Harry Gordon. "After the event, she may become withdrawn, spending a long time on the loo - because it can take 20 minutes to empty the bladder."

Historically, we in the West are no strangers to female circumcision. Clitoridectomy was practised in Victorian England to "treat" mentally ill women, while it has been used within living memory in America to "cure" masturbation. The practice has now died out here, but around the world there are some 100 million women and girls who have been circumcised, mostly in parts of Africa and the Middle East.

On a recent trip to Mali with the development charity Plan International, I visited the village of Sikoro to talk with local people about what they call "excision" (the term "genital mutilation" is seen as insulting by Malians, who genuinely believe they are doing the best for their daughters). We were warmly welcomed among the mud huts with a festival of music and dancing before being taken to meet the Imam, a Sunni Muslim with three wives and 11 children. (He asked not to be named because - controversially - he is against excision and wants to avoid conflict with other religious leaders).

"The Prophet was a very tolerant man, and in the Koran excision is not an obligation," he said. "One of its consequences is sterility; another is diminished sensitivity for a lady, which is a bad thing. To have a baby is already difficult, but excision makes it worse. Yet a lot of people are in favour. Change is a very long, slow process and we cannot expect old people to accept this. Since my niece had to go to hospital to stop excess bleeding after excision I have stopped excision for my daughters, but I have had clashes with my wives, who are not convinced yet."

Then a lively, humorous old lady with a wide, toothless smile comes forward to meet us. She is Sokolonba Kante, excisor for Sikoro and many nearby villages. "It is my family tradition," she says. "I got my knife from my grandmother, who taught me. It is my job; I am asked to do it. When people see me they say 'There goes our good old wife,' because they know I perform it well. I can excise 40 girls in a day without any problems because I am an expert.

"There is no anaesthetic. I use traditional remedies against infection (a herbal antibiotic) which I apply to the part for three days. I use alcohol to sterilise the knife. I don't remove all of the clitoris and I know where to stop. I excise all ages - from babies to 20 years old. Girls who have not been done have come to me for excision before marriage because the other wives will humiliate them."

Just over a year ago, however, Sokolonba was persuaded to stop doing excision by Amsopt, an organisation of Malian women who are "opposed to harmful traditional practices" and who are supported by Plan. "Excision was my only source of income and I used to get oil, cloth, millet, rice and money," says Sokolonba. "Then the women in the organisation convinced me it was bad and promised me help to earn a living another way. I am still waiting but the money hasn't come yet - so I may have to start again!"

Then I am beckoned to the ecole communitaire (a schoolroom built by Plan), where a little girl of six was waiting. Her name is Bintu Sako, the Imam's niece who nearly died after excision as a toddler. Madame Diarra, a doctor working for Plan, asks her to lie down on a bench and peers between her legs. "Look, the clitoris has gone entirely," says Madame, "and when she gets married she will need another operation to open the vagina." What I see is a smooth area which reminds me of a Sindy doll, with an orifice no bigger than her little fingernail.

We try to reassure Bintu, who is crying silently. "She fears it will happen again," says Madame Diarra, but within seconds the little girl is on her feet again, being cuddled by the women. Her grandmother, who is the Imam's mother, has joined us. "When she was excised she had a lot of bleeding problems," she confirms. "But excision is our tradition. The clitoris grows long if we don't remove it, like the male part. And in order to be clean and to wash yourself it must be removed."

Madame Diarra argues with her good- naturedly, while as the only non- excised woman in the room I assure the grandmother that mine hasn't grown long. It's another myth. The grandmother says she will think about what she has heard - but did we know that in the Congo the women hang weights on their female parts until they grow long like an elephant's trunk? And then we all have a friendly lunch together, hot patties of toh (millet) dipped in a sauce of okra, cooked by the village women.

Back in England, I tell Harry Gordon about what I have seen, and none of it surprises him - except the sheer numbers excised by Sokolonba at one time with the same knife. "What a way to spread Aids and hepatitis," he sighs.

The Plan staff in Mali made clear to me that excision will only change when African women want it to change - which explains their strategy in supporting local women who tackle the health issues with their peers. "Excision is a very complex issue involving traditional African culture, modern culture and the legacy of colonial culture," Amsopt's director, Sidibe Maiga, told me. "Educated people in Mali are now against excision, but to eradicate it we need a better position for women, who remain mostly illiterate." Plan works towards this aim by freeing women in Mali from the long hours spent fetching water and grinding millet by providing wells and grain mills - so that they will have time to go to literacy classes, a first step in health education.

And Plan has already scored a major triumph, persuading 25 excisors to down tools last year in the capital, Bamako. In a televised public ceremony, the leader of the local excisors placed her stubby, blackened knife into a basket held by the Prime Minister's wife. Those excisors now run small businesses, part-funded by Plan, or they work for Amsopt, educating local women against excision in the villages.

Harry Gordon too thinks that change will follow the increasing contact between African and western cultures. If peace is restored to the Horn of Africa, perhaps the (mostly middle-class) Somali women he has treated will return home. "Maybe they will begin a women's movement against these traditional practices," he says. "The message seems to be getting through that battling against scar tissue is no way to have intercourse"n For further information about Plan's work in Mali, telephone 0171 485 6612.