THIS is the story of Fachi Escobar.

It was told to me in her own words. After almost 30 years covering the world's conflicts, it is one of the most horrific accounts I have ever documented as a reporter. Aside from its discomfiting graphic details, perhaps most troubling is the way Fachi's story so easily mirrors that of many women subjected to the sexual violence that accompanies war.

The telling of Fachi's story is timely even if difficult to comprehend in its terror, pain and suffering. Timely, because this week sees the biggest global meeting ever convened on the issue of sexual violence in conflict. Co-chaired by Foreign Secretary William Hague and actress-director Angelina Jolie, The Global Summit to End Sexual Violence in Conflict - held in London on Tuesday - will bring together legal, military and judicial practitioners as well as representatives from multilateral organisations, NGOs and civil society.

Fachi's story, though, is what lies at the heart of the summit. Her willingness to recount the events she and her family experienced stems from a desire for the world at large to understand what women like her have gone through.

Her story begins in the northern Colombian town of Apartado. It was there the three traumatic events that were to shape her life started to unfold. The first of these was the violent death of her husband. The second, the gruesome killing of her son. Finally, she herself would become a victim of torture and sexual abuse.

For going on 50 years Colombia has been subjected to Latin America's longest running conflict, in which left-wing guerrilla groups, right-wing paramilitaries and the country's government and armed forces have slogged it out in a bitter and barbaric struggle. It was against this backdrop that these dark chapters of Fachi's life were enacted.

It was in October 1997 that gunmen from the infamous right-wing Bloque Bananero paramilitary group picked up Fachi's husband, Moises Antonio Castillo. They did so simply because he had helped local authorities recover the bodies and fingerprints of other banana workers massacred by the paramilitaries for having the audacity to try to unionise or were perceived to have sympathies with rival left-wing groups.

"He was tortured in the worst way, they pulled his eyes and toenails out when he was still alive," Fachi told me the day we talked in Apartado. We had agreed to meet in the offices of Pastoral Social, a church group that works with the Scottish Catholic International Aid Fund (Sciaf) in supporting the victims of sexual violence.

In this office Fachi described how the death of her husband was to set in train subsequent events that would tear her family apart in the most terrible way imaginable. Among those who went to search for her husband's body was her nine-year-old son Juan. The scream he gave on finding his father's mutilated body marked the beginning of a lifelong trauma that left him with speech difficulties.

"My son is now 27 years old and he is like a child. He still wets the bed and sucks his thumb," says Fachi, who still bears the mental scars of seeing her husband's body in the hospital "without eyes and nails".

Unable to take her husband's body away for burial, in the days that followed a black car would regularly park outside her home, posing a threat and warning. Afraid for her family, Fachi fled with her children to start a new life 100 miles to the north, in her home town of Arboletes.

Here it was a struggle to survive and her youngest son Moises jnr at the age of just 14 took a job in a garage to support his mum's work as a cleaner. It was not legal but they had nothing to eat. Here, Fachi was also warned not to try to claim compensation for her husband's death as she too would be killed. Later, while studying to be a car mechanic, Moises jnr made a visit to the union office in Apartado that represented his father to try to establish why he had been murdered. By now the whole family had returned to the city.

One afternoon Moises jnr told his mum he was going out for cigarettes, moments later he was shot in the head just outside the home. Moises jnr was 17 years old and eye-witnesses said his killers had laughed as they robbed the teenager's body of a necklace and his shoes. "The bullet took out his eye. I found him in a pool of blood and I thought he was drowning," Fachi recalls, before telling how she then became very sick and her life became totally "damaged". Later, a paramilitary boss named Perdo Padilia informed her that Moises jnr had been killed to prevent him finding out who had tortured and murdered his father.

But the paramilitaries who stalked Fachi's life were not finished yet. Back once again in Arboletes, Fachi took a job on a nearby ranch and farm. There she milked cows and helped make cheese, but at the same time came to the attention of a paramilitary chief who wanted to recruit her 14-year-old sister Deinani as a child soldier. Fachi had the youngster sent away for safety and, as a result, was to be targeted.

"One day I saw some men on horses, they crossed a creek near my house and they carried guns and had their faces covered with ski masks," Fachi told me, her body language suggesting she was bracing herself for recounting what followed. "You put your sister away so you are going to pay for that," the chief gunman told Fachi, who by then was seven months pregnant, expecting another son by her second husband. What followed next as the gunman pushed Fachi into a bedroom was to further indelibly scar her for life.

"He ripped my clothes, raped and sodomised me, the other men did the same," Fachi recalls, describing those terrible moments of her ordeal in such graphic detail that my Colombian interpreter found himself struggling emotionally to continue translating. Bleeding profusely from her wounds, Fachi was told in hospital that her baby was lost. Another son gone, along with her first husband, and now she herself a victim of paramilitary atrocities.

So traumatic was the impact of her rape that her second husband was himself unable to come to terms with what Fachi had undergone and the couple eventually split up. Such an outcome is not unusual in Colombia's rural communities and indeed in other parts of the world, where the victims rather than the perpetrators are often stigmatised.

It was at this moment, however, that this courageous, remarkable woman decided to devote herself to working with other victims of sexual violence in Colombia's conflict. "I now live with my granddaughter and we are involved in the victims' programme," she says proudly. She then mentions one last sting in the tail in a life full of suffering. "I have throat cancer and it is just my granddaughter and me now."

Fachi's experience is not uncommon in countries wracked by war. In Colombia, where political violence is still widespread, there is also a culture of impunity for many perpetrators of sexual war crimes.

"One day I was in the bus station with my step-daughter and I saw one of the paramilitary gunmen who raped me," Fachi continues, describing how the man leaned over lewdly and told her: "Your daughter is very hot."

Fachi filed a report at the local justice office in Apartado, but nothing was ever followed up or done by the authorities who themselves are frequently either inextricably connected to the paramilitaries or run in fear of them. In Colombia, there is no official registry that collates specific data on the number of women and children who have been victims of sexual violence in the context of the country's conflict.

Efforts have been made by women's NGOs to document crimes, with the most comprehensive study to date being that of the campaign Rape and Other Violence: Leave my Body out of the War.

Their study spans 2001-09 and finds that on average, 54,410 women every year - 149 every day, or six women every hour - suffered from sexual violence in Colombia.

These figures support the findings of the Constitutional Court that sexual violence constitutes a "systematic, habitual and generalised practice" in Colombia's war.

Throughout history, women's bodies have been used in conflict to achieve military objectives and as spoils of war. In Colombia, however, a distinctive use for sexual violence against women is also prevalent, that of exercising social and territorial control. Even after many paramilitary groups in the country were demobilised, their members' re-emergence in overtly criminal gangs mean their atrocities and crimes continued.

As a report by the human rights monitoring group ABColombia points out, the magnitude of conflict-related sexual violence against women in Colombia is yet to be fully understood. It is a crime that is massively under-reported, as indeed it is in many parts of the world. It is this documenting and gathering of evidence that this week's unprecedented summit in London will focus on.

According to the organisers their aim is "to create a sense of irreversible movement towards ending the use of rape and sexual violence in conflict".

Across the world, women encounter major obstacles to accessing the justice system amid extremely high levels of impunity for perpetrators of crimes against them. Yet, despite this and at considerable personal cost, many like Fachi Escobar bravely speak out, demanding rights to truth, justice and reparation.

In doing so they often have to endure yet more threats and risk to their physical security and to that of their families.

As Fachi faces the last years of her life she continues daily to face the terrible trauma of the past. "I still have nightmares, and one night I even thought I saw my husband's eyes at the door," she told me before explaining what keeps her going. "I struggle for my children and grandchildren. Who else is going to help them?"

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