Andrew Soper, 74, the abbot of Ealing Abbey from 1991 through to 2000, was headmaster and senior priest at St Benedict's School, in Eaton Rise.
The priest, known as Father Laurence, is on trial at the Old Bailey and faces 19 charges of child sex abuse against 10 boys in the 1970s and 80s following his extradition to Britain.
The boys, who cannot be identified for legal reasons, were allegedly subjected to sexual touching and beaten with a cane.
In a taped interview played in court, the complainant said he would get “flashbacks” about Soper.
“It's a nightmare that is waking me up at the moment,” he said. “I wake up absolutely soaking in swear and the bed is wet.”
Explaining why he never told anyone or sought medical help after Soper had sex with him, he added: “I could not do it.
“A couple times he really hurt me, but I couldn't do it. I was too embarrassed.
'You couldn't do anything about it'
“It was the way he manipulated you so you could not tell anyone and it got to the stage where you were damned if you did and you were damned if you didn't.
“If I had told a doctor a priest did that, I would have got the s*** beaten out of me by the Father.
“They wouldn't believe you. You couldn't do anything about it.”
When asked if the alleged abuse always took place in Soper's office, the witness described one occasion when the priest had “fondled” him at a youth hostel during a trip to Cheddar Gorge.
The man also told the court Soper would “stalk” the playground and order youngsters to come and see him after dinner.
Asked how many boys he would beat on a “typical day”, the witness said: “We don't know.
“I would say he was very into that sort of thing.”
Violence and abuse 'sadly prevalent'
Jurors have heard the school came under scrutiny in the past, with “both violence and sexual abuse” by the adults in charge said to be “sadly prevalent”.
The court heard Soper quit as an abbot in 2000 and moved to Rome, during which time alleged victims started to come forward.
Soper was interviewed under caution upon his return to Heathrow in 2010, but subsequently failed to attend further appointments.
On Wednesday (October 11), the court also heard Soper – who is no longer a monk but remains a priest – spent six years living in Kosovo, with a European Arrest Warrant issued for his extradition.
The trial continues.
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