They won't show their faces to the camera because, they say, they still have friends and family being held by the fanatics and they fear the repercussions that they might suffer if they reveal their identities. It is hard to imagine what could be worse than what they have already routinely suffered.
"We were raped up to five times a day," says 20-year-old Bushra. "One girl went to the bathroom and slit her wrist. When she did not die she cut her throat. The guards came to me and said you come and identify her - she's your friend. I could not recognise her. There was so much blood on her face. The guards wrapped her in a blanket and threw her out with the rubbish."
Selection processAs they advance through huge swathes of Syria and Iraq, IS commanders are ridding their territories of all religious minorities that would compromise their vision of a new Caliphate, ruled by Sharia law and unsullied by the infidel. The Yazidis are neither Muslim Christian but worship a peacock god which, in the eyes of the Islamic State group, make them devil worshippers and a valid target for extermination.
Bushra shivers at the memory of the attack on her village, almost exactly a year ago.
"One night they attacked two nearby villages. There was fighting up to 6am. Our relatives in a nearby village told us to leave as there were no Peshmerga fighters, only Yazidi men. But the Peshmerga in our village told us to stay and not to worry as they would protect us." But Kurdish Peshmerga forces failed to hold back the IS fighters and they entered the village.
Twenty-one-year-old Noor takes up the story. "They separated the men from the women and children. They took the men away to be shot. I have seven brothers - one managed to escape. The other six are still missing. My mother was taken with 70 of the older village women. We saw a digger arrive and heard shots." Only young women were spared and many of those wish they hadn't been.
Sixteen-year-old Munira says they were then herded in to a classroom in the village school and the selection process began. "The IS commanders are between 50 and 70 years old. I was 15 when I was selected by a commander. He said younger girls are better than older ones. They usually select the most beautiful and youngest girls for themselves."
After a few weeks, he got bored of her. "Abu Mohammed said, 'I had this girl when she was a virgin. I am bored of her now. I want another one.' I was sold to Abu Abdullah who also raped me. He got bored with me after a few days. He sold me to Emad. If I had not escaped he would have sold me on as well."
BrutalityThey were all beaten and raped daily throughout their captivity. Traumatised and exhausted, they nonetheless seized every opportunity to try to escape. Noor was found trying to climb out of a window by her abuser, Salman, who pulled her back and told her she would be punished.
"Salman and his guards attacked me. They hit me and burnt me with cigarettes. Salman told me to undress. He said, 'I warned you not to escape now you will know your punishment.' He let the six guards in, locked the door. They raped me brutally. I do not know how many times."
All three girls eventually escaped and were living in IDP (Internally Displaced People) camps in Iraq when the UK-based charity, AMAR Foundation, arranged for them to come to the UK to tell their stories and to help deter young British Muslims from going to Iraq to join IS.
Noor, Bushra and Munira sit opposite three teenagers from the Bristol City Academy.
Soon after the attack on the Yazidis, 15-year-old Yusra Hussein, who was studying for her GCSEs at the academy, left to join IS.
Eighteen-year-old Nasra Ahmed says she's in contact with Yusra and others who have joined IS through social media. She says "they say they have a nice house, a husband, money, everything a 15-year-old would want." "It is all lies," Noora says angrily,
"They promise them a nice house, servants and a car but they lie again." Another Bristol girl, 14-year-old Ikram Hassan, asks "what advice would she give to the other girls who want to join IS?" "My message is, don't go!" says Munira. "You will be raped and beaten and sold to other men. They are criminals."
At another academy, in Birmingham, teachers and community leaders are trying to get this message across with a campaign called Open Your Eyes in which they show videos of IS atrocities.
The mainly Muslim pupils at the school watch politely but they begin to look really interested when the three young Yazidis walk in to the room to address them. Nadia tells them about the rapes and killings and says to the assembled pupils, "I feel that I am dying inside when I hear about them going there. I would not wish what I have seen and been through on anybody."
The pupils are visibly shocked. One apologises on behalf of the majority of peace-loving Muslims for the attacks on the Yazidis. This direct contact with young women of their age has clearly had an effect. Sadly, the three young Yazidis have to return to Iraq the next day.