In 2012 an Indian student was violently raped on a moving bus in Delhi and died of horrific internal injuries. Leslee Udwin spoke to one of the rapists on death row while spending two years making a film about the case. She came away shocked by India's treatment of women - but inspired by those seeking change.
The horrifying details of the rape had led me to expect deranged monsters. Psychopaths. The truth was far more chilling. These were ordinary, apparently normal and certainly unremarkable men.
On 16 December 2012, the 23-year-old woman had been to see a film, the Life of Pi, with a male friend. At 8.30pm they boarded an off-duty bus, with six men on board, five adults and a juvenile. The men beat the friend and each raped the woman in turn, before assaulting her viciously with an iron instrument.
Mukesh Singh, the driver of the bus, described to me every detail of what happened during and after the incident. While prosecutors say the men took turns to drive the bus, and all took part in the rape, Singh says he stayed at the wheel throughout.
Along with three of the other attackers, Singh is now appealing against his death sentence. In 16 hours of interviews, Singh showed no remorse and kept expressing bewilderment that such a fuss was being made about this rape, when everyone was at it.
"A decent girl won't roam around at nine o'clock at night. A girl is far more responsible for rape than a boy," he said.
"Housework and housekeeping is for girls, not roaming in discos and bars at night doing wrong things, wearing wrong clothes. About 20% of girls are good."
People "had a right to teach them a lesson" he suggested - and he said the woman should have put up with it.
"When being raped, she shouldn't fight back. She should just be silent and allow the rape. Then they'd have dropped her off after 'doing her', and only hit the boy," he said.
Chillingly, he went on: "The death penalty will make things even more dangerous for girls. Now when they rape, they won't leave the girl like we did. They will kill her. Before, they would rape and say, 'Leave her, she won't tell anyone.' Now when they rape, especially the criminal types, they will just kill the girl. Death."
I had the long and shocking list of injuries the young woman had sustained, read out to him. I tried, really hard, to search for a glimmer of regret. There was none.
It would be easier to process this heinous crime if the perpetrators were monsters, and just the rotten apples in the barrel, aberrant in nature. Perhaps then, those of us who believe that capital punishment serves a purpose, and I am not among them, could wring their hands in relief when they hang.
For me the truth couldn't be further from this - and perhaps their hanging will even mask the real problem, which is that these men are not the disease, they are the symptoms.
My encounter with Singh and four other rapists left me feeling like my soul had been dipped in tar, and there were no cleaning agents in the world that could remove the indelible stain.
One of the men I interviewed, Gaurav, had raped a five-year-old girl. I spent three hours filming his interview as he recounted in explicit detail how he had muffled her screams with his big hand.
He was sitting throughout the interview and had a half-smile playing on his lips throughout - his nervousness in the presence of a camera, perhaps. At one point I asked him to tell me how tall she was. He stood up, and with his eerie half-smile indicated a height around his knees.
When I asked him how he could cross the line from imagining what he wanted to do, to actually doing it - given her height, her eyes, her screams - he looked at me as though I was crazy for even asking the question and said: "She was beggar girl. Her life was of no value."
These offences against women and girls are a part of the story, but the full story starts with a girl not being as welcome as a boy, from birth. When sweets are distributed at the birth of a boy, not of a girl. When the boy child is nourished more than the girl, when a girl's movements are restricted and her freedoms and choices are curtailed, when she is sent as a domestic slave to her husband's home… If a girl is accorded no value, if a girl is worth less than a boy, then it stands to reason there will be men who believe they can do what they like with them.
I spoke to two lawyers who had defended the murderers of the 23-year-old student at their trial, and what they said was extremely revealing.
"In our society, we never allow our girls to come out from the house after 6:30 or 7:30 or 8:30 in the evening with any unknown person," said one of the lawyers, ML Sharma.
"You are talking about man and woman as friends. Sorry, that doesn't have any place in our society. We have the best culture. In our culture, there is no place for a woman."
The other lawyer, AP Singh, had said in a previous televised interview: "If my daughter or sister engaged in pre-marital activities and disgraced herself and allowed herself to lose face and character by doing such things, I would most certainly take this sort of sister or daughter to my farmhouse, and in front of my entire family, I would put petrol on her and set her alight."
He did not disown that comment when I put it to him. "This is my stand," he said. "I still today stand on that reply."
Gender-inequality is the primary tumour and rape, trafficking, child marriage, female foeticide, honour killings and so on, are the metastases. And in India the problem is not lack of laws - after all, India is a democracy and a civilised, rapidly developing country. The problem is implementation of them.
Article 14 of the Indian Constitution confers absolute equal rights on women. The giving of dowry is a legal offence, but many families maintain the custom nonetheless. Until and unless the mindset changes, the cancer will thrive and continue to spread.
But what compelled me to leave my family and go to Delhi to make this film was not the rape itself, nor the horror of it. It was what followed.
Starting on the day after the rape, and for over a month, ordinary men and women came out on to the streets of India's cities in unprecedented numbers to protest. They braved a freezing December and a ferocious government crackdown of water cannons, baton charges, and teargas shells. Their courage and determination to be heard was extraordinarily inspiring.
There was something momentous about their presence and perseverance - reminiscent to me of the crowds that had thronged Tahrir Square in Cairo - a gathering of civil society that demanded a conversation that was long overdue.
It occurred to me that, for all its appalling record of violence against women and relentless rapes, here was India leading the world by example. I couldn't recall another country, in my lifetime, standing up with such tenacity for women, for me. And I knew at once that I simply had to use whatever talents and skills I had, to amplify their cries of "enough is enough!" which were reverberating across the whole world.
As is often the case with extremely challenging endeavours where the human stakes are high, the main struggle for me was the emotional and psychological toll the work imposed.
When you look into the blackest recesses of the human heart, you cannot but be depressed and deeply disappointed. I woke one morning on the shoot, wet from head to toe, bathed in sweat and fear and my heart knocking against my ribcage. This was a panic attack. I phoned home thinking my husband would answer, but my 13-year-old daughter, Maya, did.
She immediately sensed I was in trouble. And when I told her, in tears, that I was coming home because this was too big for me, the mountain was just too high to scale, she said: "Mummy, you can't come home because I and my generation of girls is relying on you."
What carried me through, apart from Maya, was what had inspired me in the first place: the new-thinkers, especially among the youth, in India who want change and are clamouring for it. And I am absolutely optimistic that we are now on the cusp of change.
India's Daughter will be broadcast on Storyville on BBC Four on Sunday 8 March at 22:00 GMT.
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