In a country that has outlawed homosexuality, Frances Harrison meets one Iranian cleric who says the right to a sex change is a human right.
For 20 years Mahyar has been a woman trapped in a man's body.
As a small child Mahyar liked dressing up in women's clothes and experimenting with make-up but as she grew older it got more difficult. "I badly needed to do it but it had to be in secret," she says.
Now she wants to have a sex-change operation - if she can muster the Â£2,000 it will cost in Iran. If her family doesn't help financially, she says she might sell one of her kidneys to pay for it.
"People say you'll get other illnesses but I think I can live without one kidney. I cannot live between the sky and the earth," says Mahyar.
Surgeons have already removed Mahyar's testicles. After the operation, her older brother locked her up for a week and wouldn't let her use the telephone. Mahyar's brother says someone has put a spell on her.
When Mahyar wants to feel normal she goes to the clinic of Dr Mirjalali - Iran's leading sex-change surgeon. There are women who were men, men who were women and those like Mahyar waiting for the operation they believe will be a sort of rebirth.
Dr Mirjalali says in Europe a surgeon would do about 40 sex change operations in a decade. He's done 320 in the last 12 years in Iran.
"If you saw them out in the street you wouldn't realise that one day they were the opposite sex," he boasts.
The doctor will use parts of Mahyar's intestines to create female sex organs. He warns it involves five or six hours of difficult surgery and weeks of painful recuperation.
Mahyar loves to go to cosmetics shops - and try out new nail varnish for her long manicured nails and discuss with the amused female shop assistants the best sort of foundation cream to hide her stubbly chin.
I want to suggest that the right of transsexuals to change their gender is a human right - Hojatulislam Kariminia - Cleric
The sight of a man wearing make-up does turn heads on the street. Islamic tradition does not allow cross dressing - a man should only dress in male clothes. But that is not to say Iran's religious scholars are antagonistic to transsexuals.
Hojatulislam Kariminia wrote his doctoral thesis on the implications of sex-change operations for Islamic law.
He is a leading expert on questions like does a husband or wife need the permission of their spouse before a sex change operation? Is their marriage automatically annulled afterwards and what happens to the wife's dowry money or inheritance if she becomes a man.
He shows me the book in Arabic in which, 41 years ago, Ayatollah Khomeini wrote about new medical issues like transsexuality.
"I believe he was the first Islamic scientist in the world of Islam who raised the issue of sex change," says Hojatulislam Kariminia.
The Ayatollah's ruling that sex-change operations were allowed has been reconfirmed by Iran's current spiritual leader.
That has meant that clerics like Hojatulislam Kariminia can study transsexuality - unlike homosexuality which is completely forbidden in Islam and illegal in Iran.
"I want to suggest that the right of transsexuals to change their gender is a human right," says the cleric, who is so fascinated by the subject that he says he dreams about the transsexuals he has studied at night.
"I am trying to introduce transsexuals to the people through my work and in fact remove the stigma or the insults that sometimes attach to these people," says Hojatulislam Kariminia.
That's not easy. In every way Alan looks like a man but he was born Alim - with a woman's body. Three years ago he had a sex-change operation.
"I don't remember who Alim was - what she used to do, what kind of personality she had," says Alan. The past is something he'd prefer to forget.
Alan was about to get married when the parents of his bride found out he had been born a woman. They were horrified and refused to allow their daughter to marry what they considered another woman.
Iranian society has yet to catch up with its religious leaders - who say transsexuality is an illness like any other for which Islam has the solution and science the cure.
Alan shows me his new birth certificate and passport, which has been legally changed to say he is now a man. He's surprised to learn in Britain a transsexual who's had a sex change operation cannot change his or her gender on their birth certificate.
"I think in Iran it is better; in Iran they say you need to know your identity - either you have to be a boy or a girl," says Alan.
The Gender Recognition Act 2004 comes into force in the UK in from April 2005. Under the provisions of the Act a transsexual person can apply to be legally recognised in their acquired gender.
Frances Harrison's film will be screened on Thursday, 6 January, 2005.
Newsnight is broadcast on BBC Two at 10:30pm every weeknight in the UK.
Story from BBC NEWS: Published: 2005/01/05 17:07:32 GMT Â©BBC MMV
by Frances Harrison
BBC's Tehran Correspondent