Two Australian monks were found guilty of sexually abusing their students at the now close Fort Augustus Abbey School in the Highlands and its feeder school at Carlekemp in east Lothian.

The acts of sexual abused happened several decades ago, but it was only during this time that BBC Scotland was able to unearth details of the monks' dirty secrets through an investigative documentary to be shown on July 29, 21:00 (GMT) on BBC1 and BBC iPlayer.

The accused Australian monk was Father Aidan Duggan who taught at the school back in 1953 and 1974.

The victim who was willing to share his dark past with the monks is Donald Macleod who was a student at the school in 1961. Father Duggan was his piano and photography teacher.

Mr Macleod was only 14 years old at the time of the abuse.

"At the time I just felt very very lonely... I remember that he was... very friendly and when I was playing he'd put his hand on my knee ... which at the time I thought was rather nice, being friendly," Mr Macleod told BBC.

However, he was then seriously sexually abused by Fr Duggan. He immediately called the authorities' attention, but no one believed him.

"I was called into the headmaster's office and he said that he'd heard that I'd been telling my parents about Father Aidan and that I shouldn't tell these lies and that it's a mortal sin to lie about things like that. And if you commit mortal sin you go to hell."

Two other victims of Fr Duggan were brothers Christopher and David Walls who were both students at Carlekemo in the 1950s.

"I was being groomed... the beatings stopped, the sarcasm and the making a fool of you in public and so on, that all stopped, once the cuddling started. So it was a huge relief. And, you definitely felt this kind of sense of gratitude almost," Mr Christopher Walls told BBC.

David's brother Christopher Walls suffered the same plight. "And it wasn't until later that it fell into place... that was what it was all about - all the beatings and all that was about this," he said.

BBC was able to track another victim of Fr Duggan in Australia named John Ellis.

Mr Ellis told BBC that he was sexually abused by Fr Duggan from the age of 13.

"It got to a point I knew that I was in a situation that I didn't want to be in, and I didn't know how to get out of it."

Fr Duggan went back to Australia in 1974, but the Benedictines authorities gave no warnings about him. He still became a parish priest in Sydney and continued to abuse children. He died in 2004.

The investigative documentary also featured victims of another Australian named Fr Chrysostom Alexander, now 77 years old and living in Sydney.

He had abused a student in 1977. The student said that after the abuse, Fr Alexander swore and drove him out of the room. Later he was told not to tell anyone of what happened.

The student told his parents and his parents reported the incident to the school.

However, Fr Alexander was also sent back to Australia without any warning.

BBC reporters were able to track Fr Alexander at his home, but the monk refused to comment.