"Still now they follow me": Footage of Banaz Mahmod warning police before her 'honour' killing to be shown for the first time

The camera mounted in the corner of the police interview suite captures the nervousness of the young woman as she flicks hair away from her face and starts to recount her grim story.

Recorded on grainy videotape with the time code running beneath, Banaz Mahmod quietly details a litany of sexual violence and oppression at the hands of an abusive husband. She tells of intimidation by men on the street that she recognises, but does not know, when she finally left him. Then finally, she appears to warn of her own impending death – because of the "dishonour" she has brought on her family.

"Still now they follow me," says Ms Mahmod in clipped English, heavily-accented from her early years in the Kurdish region of northern Iraq. "That's the main reason that I came to the police station. In the future at any time if anything happens to me, it's them."

The footage – to be shown for the first time next week after lying unseen by the public for seven years - later became evidence for investigators after her warnings about the danger she faced went largely unheeded.

It took one police officer three months to write up the report of her account. Within two weeks of her signing it as a true record, Banaz Mahmod was dead – killed, and possibly raped, in her parents’ house by a gang of killers in January 2006 employed by the family in one of the country’s most high-profile so-called "honour" killings.

Her body, folded up and hidden in a suitcase, was buried hidden underneath a freezer in the garden of a house in Birmingham. The footage – which will be shown as part of a new film-documentary about the case - demonstrates in graphic and disturbing detail the terrifying ordeal of a young woman who defied the deeply-entrenched conventions of her patriarchal society to leave her abusive husband and start a new relationship.

The ‘them’ to whom she refers were members of her family and the wider Iraqi-Kurdish community, enraged at the decision to divorce a man who acted as if she were a "whore" and treated her like "his shoe and he would wear it just whenever he felt like it", according to her recorded interview. She tried to leave him on a number of occasions, but went back to try again at the urging of her family, who – despite her obvious suffering and repeated complaints of marital rape – likened him to the "David Beckham of son-in-laws".

The recorded interview was one of five contacts with police in the five months before she died in January 2006. On one occasion, she handed over a letter at a south London police station naming the men who she said were ready to kill her and her boyfriend, Rahmat, whom she had been spotted kissing in contravention of the code of honour demanded by the male-dominated members of her family and community.

The repeated failures of police in the case – her husband was not sought or interviewed before her death it was revealed in a police watchdog report – led to significant change in the way such honour-crime cases are treated.

The Banaz case was eventually properly investigated by a dogged team of Metropolitan Police officers who not only secured the convictions of Ms Mahmod’s father and uncle, but also brought back two cousins from northern Iraq who carried out the killing and who had lived for several years protected in northern Iraq.

But despite changes and improved training, campaigners said yesterday that the system remained ill-equipped to deal with deep-seated practices that remain hidden in communities partially closed off to outside scrutiny.

Police investigating the Banaz case were hampered by repeated attempts by elements within the community to derail the inquiry with false witness reports, and sightings. "If Rahmat hadn't reported her missing, we wouldn't have known," says Detective Superintendent Caroline Goode, who led the successful inquiry. "You have to ask how many of those are going on in this country. It could well be that we’re only seeing the tip of the iceberg."

There is little evidence of the scale of the problem with police under no statutory requirement to record honour-based crimes. A series of freedom of information requests by IKWRO, the Iranian and Kurdish Women’s Rights Association, reported last year that police recorded more than 2,800 incidents of honour-based violence in 2010. Yet Karma Nirvana, an organisation set up to support victims of honour crime and forced marriage, said that more than half of the near 600 calls they received every month do not report an incident to their police, doctor or other agency.

The UN in 2000 estimated there were 5,000 honour-based killings worldwide, the most brutal form of censure against women who are seen to have brought shame on a family or community. While most cases are in South Asia or the Middle East and predominantly from within Muslim communities, cases such as that of 19-year-old Banaz Mahmod brought to light the tensions within immigrant communities struggling to adjust to changes in lifestyle.

"Honour is the prime social currency within this community," says Deeyah, a Norwegian-born pop star turned campaigner who spent years making the film about Banaz Mahmod. "If you are treated like a second-class citizen in a country like Britain, where are you going to exert your manhood and control? You are going to do it at home.

"Some people are clinging on to this mentality and these processes that in many cases their parents have left behind."

Some groups suggest that thousands of honour-based crimes continue unseen within minority communities in Britain. Hundreds more women are taken abroad where they are forced into marriage or suffer serious harm when their westernised world view of life, sex and relationships places them in conflict with their traditional male-lead communities.

The disputes often come to a head during the child’s adolescence, which is when they are packed off to the Asian subcontinent for marriage. "Some don’t come back, some are left there," said Jasvinder Sanghera, the chief executive of Karma Nirvana. "We don’t have a handle of how many people there are."

The Foreign Office runs a forced marriages unit, which works with its embassies and local police to rescue hundreds of British women being forced into marriages and brought back to the UK. But until now, there has been no attempt to track the women once they return to the UK; many would have been coerced to travel by families in the first place.

Social services and the education authorities have proven to be woefully ill-prepared to address the issue and in many cases have failed to report the failure of youngsters to return from "summer holidays", says Ms Sanghera. She has learned of one case where a teacher put up posters in her multicultural school highlighting concerns of overseas forced marriage – only to have them taken down by the head. "The head didn't want to offend the Muslim parents," said Ms Sanghera.

The authorities are complicit in the crimes by failing to respond to the abuses within their communities, says Deeyah, from a Punjabi-Pashtun background. She suffered “honour” abuse during her career, forcing her to leave her native Norway and then Britain. "British and western authorities feel nervous about grabbing this issue," she says. "They are scared. If women are dying, we cannot afford to be polite about that."

In her recorded interview, Banaz tells the sole police officer that her husband threatened to stick a knife in her after she called him by his name in front of guests. Her husband said it signalled a lack of respect. “He was thinking like in 50 years back," says Banaz. "I was explaining we are living in Britain. I was shocked because it was just a name, it’s not going to do any harm."

She promises to get back in touch with the police if she feels she is in danger and the camera catches her as she leaves the room. The lights are switched off.

Banaz: A Love Story will be premiered at the Raindance Film Festival in London on September 29