The 61-year-old told his BBC Sounds podcast Different he witnessed and experienced sexual and violent physical abuse at the Edinburgh Academy.
He told BBC Radio 5 Live the abuse had a “profound effect on my life” and had been “obsessing me”.
The Academy “wholeheartedly” apologised and said it had helped police.
It was after his wife heard another BBC podcast, In Dark Corners, which explores abuse at Britain’s private schools, that Campbell decided to contact the producer and reveal what he knew about the Edinburgh Academy.
Introducing his 5 Live show Campbell told listeners he was about to discuss a difficult subject, adding: “I know I am amongst friends but I may have a wobble but I know you’ll be with me.”
Explaining his experiences, he said: “I was badly beaten up at school by a teacher who was a leading light in the scripture union – my mother took it as far as she could and got a grovelling apology from him, but was essentially stonewalled and it was hushed up by the school.
“Those were different times and that has stayed with me all my life.
“And there was a teacher Hamish Dawson who is now dead who had regularly wandering hands – many of us were on the receiving end – and me and my friends still talk about it – with utter contempt. We were 12.
“But there was something else that I will never forget.
“Being in a changing room at 10 years old – after rugby – seeing a teacher abuse my friend. I cannot describe it here and I can never un-see it.
“This man was known to us all as a predator and a sadist but we never told. Anyone. My school friends and I talk about it now with each other with again – contempt, disbelief and incomprehension that sort of thing happened in plain sight and nothing was done.
“And why didn’t we as little boys tell anyone in power what was happening? I don’t know.
“I made up my mind to contact the journalist Alex Renton to tell him about this man who we all presumed had disappeared into the ether and probably died.
“When I spoke to Alex, I said I have to tell you about this man and something that haunts me – I didn’t suffer at his hands – I wasn’t abused by him but I know how much it affected those who he did target.
“All their lives – there were many. What I witnessed was horrific and I realised how much it’s just a part of my psychological furniture – always there.
“I told Alex his name and before I’d got to the surname he finished it off for me. He was called ‘Edgar’ in the programme. It was an extraordinary moment. I thought of all my friends. All those little boys.
“But at last – someone told the grownups.
“And then three words that I will never forget – he is alive.
“I worked it out, given other witness statements on the record, survivors accounts – and his long career in teaching always with glowing references – he could well be one of the most prolific paedophiles in British criminal history.
“He lives abroad – with his wife in comfortable retirement and efforts to extradite him have failed. He has been arrested but can’t be charged until he is on British soil and the chances of that are receding.”
‘Deep regret’
A spokeswoman for the Edinburgh Academy said it “deeply regrets what has happened in the past and apologises wholeheartedly to those concerned”.
“We have worked closely with the relevant authorities including Police Scotland with their inquiries and would like to provide reassurance that things have dramatically changed since the 1970s.
“The Academy has robust measures in place to safeguard children at the school with child protection training now core to the ethos of the Academy.”
The Scottish Child Abuse Inquiry has heard evidence about abuse at the Edinburgh Academy, as well as other Scottish private schools, including Gordonstoun, attended by the late Duke of Edinburgh, and the Prince of Wales. That school has apologised to anyone who suffered abuse in its care.
The inquiry, led by Judge Lady Smith, was launched by the Scottish government in 2015. It will report the outcome of its investigations to Scottish ministers “and make recommendations” about policies and the law.
