Allegations that a man in a police uniform sexually abused a boy from Kincora have been heard by a public inquiry.
Graphic accounts of the litany of abuse carried out by three male staff members were also given to the Historical Institutional Abuse (HIA) Inquiry which is examining claims of a high ranking paedophile ring at the east Belfast boys home during the 1970s.
One victim, known only as KIN238, who was at Kincora for three weeks in 1977, claimed to have been taken to another property and abused by warden Joseph Mains, house master William McGrath and an unknown man in a police uniform.
After one incident he vomited, the inquiry was told.
The boy ran away and did not speak out until he told his girlfriend in 1999. He went to police after 2000, it emerged.
The HIA also heard about alleged violent gang rapes and of boys being pulled from their beds and returning drunk.
"Boys were too frightened to go to sleep for fear of what would happen to them," claimed another former resident.
There have been persistent rumours that prominent people were involved abusing boys at Kincora.
It is further claimed that the UK security services knew about the abuse but did nothing to stop it, instead using the information to blackmail and extract intelligence from the influential men - including senior politicians, judges and civil servants who were the perpetrators.
In statements, boys described being preyed upon just weeks after being admitted to Kincora.
New boys were warned that McGrath had "wandering hands" and would try to "touch them up".
Others told of how they were assaulted as they watched television, while they were in bed or were in the bathroom.
It was a frequent occurrence for some, the inquiry heard.
It was further claimed that afterwards, McGrath would walk away laughing.
Some residents described being scared to speak out, while others said they were too embarrassed or disgusted to tell welfare workers.
Another victim, R12 - who did not speak out until 1980, said: "I didn't know what I was doing was wrong, but I did not like it what he was doing. I was frightened."
McGrath, Mains and Kincora deputy warden Raymond Semple were jailed in 1981 after admitting abusing boys.
It is widely believed McGrath, who also led the shadowy Protestant paramilitary organisation Tara, was working as an MI5 agent.
Meanwhile, the inquiry heard how many victims told police police probing the vice ring claims in the 1980s of their shock and surprise.
R10, who spent four years at the home from 1973 to 1977, said: "I did not know of any politicians, police officers, justices of the peace, businessmen or civil servants being involved in any way at all with the hostel, staff or boys."
Another victim, given the cipher HIA172 said: "There's no doubt in my mind that such allegations were completely untrue," he said.
"If such things had been going on at the hostel involving the other boys I would have known of it because we all would talk among ourselves."
Meanwhile, a detective in the 1980s said alarm bells should have sounded with welfare workers earlier.
He wrote in a report, shown to the inquiry: "Once again the subject of homosexual activity at Kincora had come to the notice of a member of the social services and once again this snippet of information was not added to other intelligence.
"Collectively, this information ought to have sounded an alarm bell and initiated the inquiry earlier than the one brought about by the newspaper article which was published in 1980."
The HIA was set up by the Northern Ireland Executive in 2013 and has been examining allegations of physical, emotional and sexual abuse at state and church-run residential institutions between 1922 and 1995.
It is chaired by retired High Court judge Sir Anthony Hart, sitting alongside Geraldine Doherty, a former head of the Central Council for Education and Training in Social Work in Scotland, and David Lane, who was director of social services in Wakefield, West Yorkshire.
Campaigners had hoped to have Kincora included in the nationwide child abuse probe chaired by New Zealand judge Lowell Goddard because the HIA does not have the power to compel witnesses but a High Court judge rejected their legal challenge as "premature".
The inquiry is expected to hear evidence from former Kincora residents when it resumes next week.