Paul Kennedy, who was abused by John McClean at Dublin's Terenure College as a child, has waived his anonymity to speak out.
He described McClean as a bully who was determined to use boys for his own pleasure and took a lot of sadistic pleasure from manipulating, controlling and making sure you were repressed.
McClean, a former teacher and rugby coach has admitted sexually abusing 22 boys and was described in court today as "a premeditated predator".
He is already serving an eight-year sentence for the abuse of 23 other boys at the college.
Mr Kennedy said they tried their best to stand up to McClean but "we were children and back then he was a strong man in his early 30s. He would hold you and you were a 13-year-old boy. You know, see that sad man in there who is withered and very, very, very much an old 78-year-old, but back then he was strong".
He also described McClean as very, very difficult; a man who had a lot of power within the school and he said the school "facilitated" him and allowed John McClean to basically rule the roost so he could pick and chose.
"So, who would he pick and choose? Always the vulnerable. Always the ones he could get his way with," he said.
Mr Kennedy said he was fortunate he had lovely parents who gave him a grounding, but it still didn't take that stain away.
"Even though you would elbow him, mock him, stand on his foot," he said, "you still got those eyes from him and knew you were a target. The eyes were like controlling. If 'Doc’ gave you the eye, then we were in deep trouble."
He said they used to warn the young boys, the first years coming in about him.
"McClean used sport principally and the drama," he said.
Mr Kennedy said even though McClean had been demoted from directing plays, he would still mysteriously appear for a costume fitting, "and we all know where that went".
He said he was nicknamed the 'Doc' because he would "rub you up the wrong way". The joke was, he said, "I’ve hurt my wrist. Well drop your trousers and I’ll have a look at it for you. This was known outside the school as well."
Mr Kennedy said there were people in other schools, members of the opposite team, who ran from him and told him to 'F-off’. He said McClean was very powerful and was facilitated by the school.
"As I said in my victim impact statement, Terenure College was a safe place for paedophiles. They didn’t look after the boys but they certainly looked after each other."
Mr Kennedy said he hopes other victims will come forward. "We were children. John McClean robbed us of our innocence. We’re robbing it back. I had to speak up."
He also said the 45 victims who John McClean has been convicted of abusing represents only "the tip of the iceberg".
