Pope Benedict has held a senior position at the Vatican since 1981
When he arrives in Britain this week Pope Benedict XVI will be aware that across the globe many of his flock will have had their faith shaken by the scandal over priestly sexual abuse.
There have been multi-million dollar payouts to victims in America, judicial inquiries in Ireland and police investigations on almost every continent.
Cardinals and bishops have been forced to resign and priests have faced prison sentences.
But what did the current Pope know about some of these scandals?
Panorama has been investigating his role as Prefect of the Vatican's Congregation for the Doctrine of the Faith - the CDF - before he became Pope and before that as Archbishop of Munich.
Only a tiny number of such cases ever reached Cardinal Ratzinger's office. Most were dealt with by local churches or other Vatican offices.
But some victims are calling for a personal apology from the Pope.
'I remember clearly being abused'
"If a man is going to give us our spiritual guidance and if he made mistakes when he was younger, well come forward and say that it was a mistake," said Lisa Crenshaw, from Oakland in California.
FIND OUT MORE
Panorama: What the Pope Knew, BBC One
Monday 13 September at 2030 BST
Lisa was one of several victims of the paedophile priest Stephen Kiesle who worked in parishes around San Francisco in the 1970s.
The Kiesle case was forwarded to the Vatican after the priest was convicted of sexually abusing two boys in 1978 and suspended by the local church.
Father Kiesle then requested permission to leave the priesthood. His Bishop wrote to Cardinal Ratzinger's office in 1982, and several times after that, yet it took until 1987 for Kiesle to be laicised - or removed from the priesthood.
The reason for the delay, according to Father Tom Doyle, a church lawyer who campaigns for victims, was a ruling from Pope John Paul II that priests under 40 were not to be allowed to leave the church. Kiesle was 34 when he first applied.
"I think they saw it that if we made it difficult to impossible to get out of the priesthood then men will stay in," Father Doyle said.
The church was facing a crisis of young men wanting to leave their priestly vocations. But victims argue it was a case of the church putting its own interests ahead of those of victims.
"In reality laicising would not have stopped Kiesle from abusing, but laicising would have said that 'you're dangerous and we want to protect our children from you'," says Melinda Costello who was eight years old when Kiesle abused her in the church sacristy.
In a statement the Vatican told Panorama that Cardinal Ratzinger had done "nothing to hide any crime" and had acted "absolutely correctly."
What is the CDF?
From the Palace of the Holy Office at the Vatican, the Congregation for the Doctrine of the Faith (CDF) oversees Catholic Church doctrine.
It was established in 1542 by Pope Paul III to maintain and defend the integrity of the faith and examine and decide upon false doctrine.
Since 1968, the Head of the CDF has been known as 'Prefect'. Pope Benedict XVI, as Cardinal Joseph Ratzinger was Prefect between November 1981 and April 2005.
The CDF was given a broader mandate to address the sex abuse cases in 2001.
In the desert state of Arizona, the case of Father Michael Teta was sent to Cardinal Ratzinger's office in 1997 after a long church trial had found him guilty of abusing boys in their late teens and young men.
He was among a number of priests whose behaviour led the local church to pay out millions of dollars in settlement to victims.
The church court only charged Teta with acts against young men. But the case file sent to Rome included allegations that he had abused a boy aged between 14 and 15.
After reaching Cardinal Ratzinger's office in 1997 the appeal took a further seven and a half years to resolve, ending with Teta's dismissal from the priesthood in 2004.
The victims campaigner and canon lawyer, Father Tom Doyle, is highly critical of the delay. "There is no credible answer as to why that case sat there for seven-and-a-half years. I've never in my career as a canonist heard of a case taking that long on appeal - I never have."
The Vatican says the delay was due to the "particularly voluminous" files in the case and says such cases were speeded up after 2001 when changes were made to Canon Law under Cardinal Ratzinger's direction.
As for reporting the abuse to the police, the Bishop of Tucson, Gerald Kicanas, who took over the diocese in the wake of the scandal, told me that as far as he was aware Teta's abuse of a minor was not reported to the police by the local church.
Nor was he aware of any encouragement from the Vatican to do so.
"Today there is no question that that allegation would be reported to the police," he told Panorama. Father Teta denies all charges of child abuse against him.
This will be the first Papal visit to the UK since 1982
But the earliest case involving Pope Benedict stems from his period as Archbishop of Munich in the late 1970s.
There he chaired a meeting which approved psychotherapy for a priest who had molested children in the diocese of Essen, some 300 miles away.
After a short period of treatment in Munich Father Peter Hullermann was sent to another parish where he continued to abuse.
In 1986 he was convicted of child sexual abuse. Archbishop Ratzinger's former deputy told Panorama he accepted full responsibility for the decision to transfer the abuser without informing the police.
The question for the current Pope is whether he was told the exact nature of Father Hullermann's offences at a crucial meeting in January 1980.
If he was, then responsibility for informing the police lay with him.
But the minutes of the meeting do not disclose what was said in any discussion of Hullermann, simply recording that the request was granted.
The head of personnel in Munich, a close friend of the then-Archbishop Ratzinger, was told that Hullermann was withdrawn from pastoral work because he was "a danger" and could present legal difficulties.
The Pope has not said whether he was given any specific information at this meeting about Father Hullermann's abuse of children.
But seasoned Vatican observers say these stories from the past must be set against Pope Benedict's record since taking over responsibility for sex abuse cases in the church in 2001.
"You know his own journey has been quite remarkable," says Austen Ivereigh of the lay group Catholic Voices.
Melinda Costello was abused as an eight-year-old by priest Stephen Kiesle
"He sat down in 2001 and said I want all these cases on my desk. They began to arrive, 3,000 cases over 10 years. And he spoke later, at the time of his election as Pope, of the 'filth' in the church. I think he, more than anybody in Rome, really got it."
Pope Benedict's supporters also point to his meetings with abuse victims, his public apologies for the church's failings and the changes to church law he has introduced in order to speed up the removal of priests accused of sex crimes, as well as encouraging the mandatory reporting of abusers to the police.
However for many of the victims there remains an overriding question for Pope Benedict and all the senior leaders in the Vatican - why did it take so long to acknowledge their agony?
Panorama: What the Pope Knew, BBC One, Monday 13 September at 2030BST and then available in the UK on theBBC iPlayer.