Female genital mutilation, the cutting of sexual organs, is thought to affect 66,000 women in the UK.
Sometimes it happens when young girls are sent back to relatives in north or east Africa, but it is also thought that cutting occurs here in the UK too.
There have been no prosecutions so far - though the government says it is determined to end female genital mutilation (FGM).
Several hospital and community-based clinics in London help women who have suffered FGM, as well as one in Birmingham and another about to open in Bristol.
The NHS clinic at Queen Charlotte's and Chelsea Hospital treats more than 100 women a year who have had their sexual organs cut or sewn up because of cultural beliefs - including Filsan, 35.
Now a mother-of-three living in the UK, she was treated to a new dress in her native Somalia at the age of seven.
This was in fact a prelude to something sinister - having her organs cut.
'Legs tied together'
She told me: "It was so painful, even though I was given an injection for pain relief. When it wore off, I couldn't go to the toilet.
"We had to sleep on the floor, because we couldn't even get up and walk. Our legs were tied together with rope, so we couldn't move our legs apart. It was such a painful process.
"Then came the time for me to give birth to my first child. All I was thinking was - how can a child come from that area that is so damaged?
"It was really difficult confronting what I'd been through, but I'm really glad that I had a good therapist who could understand everything."
Filsan's memories still cause her pain. But her work for a Somali health project gives her optimism that the tide of community opinion is now turning against FGM.
She said: "People are now realising it's not a good practice and it needs to be stopped.
"A lot of work is being done in Africa, but we also have to raise awareness among communities elsewhere which have carried out FGM."
A special advertisement has run on Somali TV channels and generates lots of calls for the clinic at Queen Charlotte's. Staff there operate an outpatient clinic but are also able to help women at a GP surgery.
Juliet Albert, the specialist midwife running the service for Imperial College Healthcare, told me why some families still put their daughters through the ordeal of mutilation.
She said: "Most of the women we see are adamant they wouldn't perpetuate this practice. But there are a lot of culturally-based myths around FGM.
"Women get concerned that if their daughters don't have it, they will be excommunicated from society or they won't be marriageable.
"The problems women have as a result of FGM are urine infections, as well as a lot of pain during their periods and having sex.
"The reversal procedure is quite straightforward. We use local anaesthetic, make a small incision and sew over the edges, so the women are then a normal size for childbirth and making love."
The clinic makes referrals to social services if it believes specific girls are at risk of genital mutilation. That is welcomed by the public health minister, Anna Soubry.
She said: "We protect all our children from abuse in this country, whatever their parents' or grandparents' country of birth may have been.
"Although there have been no prosecutions yet on FGM, it's very important that we don't get some sort of token gesture. The usual standards of prosecuting for any offence have got to be met."
Ms Soubry joined the international development minister, Lynne Featherstone, in visiting the clinic at Queen Charlotte's.
Ms Featherstone recently announced a programme worth £35m which aims to eradicate FGM within a generation - both in the UK and in countries where the practice originates.
She said: "There have perhaps been issues in the past about not wanting to tread on cultural eggshells.
"To an extent it's been going on behind closed doors in this country - but this is violence against women and child abuse. It's illegal and we need to stop it.
"The government is very frustrated about not having been able to prosecute over FGM. The Home Office would like to see action on this.
"Extra work is now going on - and everyone has a duty to report something that might relate to FGM.
"France, for example, examines every girl's genitals until they are six years old. But that wouldn't be the right approach in this country - because it's not an issue for most of the population."
Both ministers realise that tackling this distressing problem is complicated, and more work is needed with schools and communities in many of Britain's big cities.