The Scottish Child Abuse Inquiry (SCAI) heard evidence from a man who attended the Moray boarding school in the late 80s and early 90s.
The witness was referred to only as Paul to protect his anonymity.
Paul said physics teacher Andrew Keir abused him when he was a teenager, after the teacher formed a friendship with him. The latest phase of Lady Smith’s inquiry is focussing on alleged abuse carried out in Scottish boarding schools.
In 2018, Keir was convicted of lewd acts against three pupils and sentenced to a year in jail.
Paul told the SCAI he had almost never spoken to anyone else about the abuse he suffered at Gordonstoun throughout his adult life, but decided to speak to the police after hearing Keir’s conduct towards other pupils was being investigated.
He said: “I couldn’t let someone stand up alone and go through all that.”
Paul said that initially his relationship with Keir in school was like a friendship, and he would take part in activities the teacher ran such as judo, canoeing and an electronics club.
He said other children warned him that Keir could be “handsy”, and the teacher would engage in impromptu judo lessons in class.
At one point, Keir invited Paul to the school’s swimming pool.
When Paul arrived Keir removed his swimming costume and invited Paul to do the same, though he decided to leave.
During another incident, Keir groped him as he was playing a computer game.
Paul told the inquiry: “I tried to block it out, I can literally still see the screen in front of me … it’s crystal clear.”
During his evidence session on Tuesday, Paul said he was aware of at least five other victims, three of whom were involved in the criminal case against Keir.
He said: “The most distressing, critical failure at the time was that Gordonstoun didn’t listen to someone who reported abuse at the start of 1989.
“Had they listened, potentially the abuse that happened to me would not have happened.”
Paul, who is now in his 40s, said the abuse he suffered at Gordonstoun had affected the rest of his life.
He said: “It’s meant I have had not a fantastic relationship with my parents.
“The abuse itself has had a long-lasting effect on relationships I have had.”
Paul also said he felt the criminal case against Keir should have been dealt with at a higher level than a sheriff court.
At Elgin Sheriff Court in 2018, Keir was found guilty of two charges of lewd, libidinous or indecent practice between November 1988 and March 1989.
Lady Smith’s inquiry continues, and is due to hear evidence from Gordonstoun’s current principal, Lisa Kerr, later this week.
Andrew Keir has also been listed as a witness at the inquiry.