The response to child sex abuse allegations was totally inadequate and ineffective, the former head of the Catholic church in Ireland has said.
Cardinal Sean Brady said he had been horrified by the unspeakable crimes and hoped a public inquiry would shed light on the church's dark history.
There was a shroud of secrecy designed to protect the reputation of the church, he said.
"These were unspeakable crimes," said Cardinal Brady. "There was a shroud of secrecy and confidentiality with a view not to destroying the good name of the church.
"The scandal that somebody who was ordained to serve people should so abuse the trust for their own pleasure was appalling and it was.
"To offset that, the scandal was kept a secret - very, very secret.
"Everybody involved would be bound to secrecy too."
He said: "You have been tasked with inspecting a dark chapter in our history. But, I am confident that your patient and diligent work will cast a welcome light of truth on this situation and hopefully lead to a better future."
The 75-year-old, who resigned as head of the Catholic church in Ireland on age grounds last year, was giving evidence to the North's long-running Historical Abuse Inquiry (HIA) at Banbridge, Co Down.
The senior cleric was fiercely criticised after it emerged he had attended meetings in 1975 where two teenage victims of paedophile priest Father Brendan Smyth were sworn to secrecy.
Their evidence was never handed over to police, allowing the west Belfast churchman to continue abusing children before he was finally jailed in 1994.
Cardinal Brady, then priest and teacher Fr John Brady, was a note-taker during the secret meeting at St Malachy's Priory in March 1975.
Even though he studied canon law in Rome he had no experience of dealing with child sex abuse scandal.
It did not cross his mind to inform the civil authorities, the Cardinal revealed.
"I wasn't aware of Smyth's history which has now emerged," he said.
"It just did not cross my mind to consider informing the statutory authorities. Now, of course it is the first thing that we would do.
"But, for various reasons it was considered that the in house way of doing it ourselves was more prompt, we thought more effective, but it was not; it did not involve the boys having to take the witness stand. We thought that we would deal with this ourselves."
The Cardinal told the inquiry he was motivated by an anxiety to stop Smyth and believed everything he heard from victims.
But, he acknowledged the church response was poor with little or no consideration for those who had been abused.
Cardinal Brady added: "I once again offer an unreserved apology to all those who suffered as a result of the crimes of Brendan Smyth."
Retired judge Anthony Hart is leading the HIA probe, one of the UK's largest inquiries into physical, sexual and emotional harm to children at homes run by the church, state and voluntary organisations.
Many of Smyth's victims had packed into the small courtroom for the hearing.
Yesterday, it emerged that gardai knew about Smyth's paedophilia as far back as 1973.
Earlier it was revealed Smyth had told a doctor in 1994 that the number of victims he sexually assaulted could run into the hundreds.