More than four decades after former Mildura police officer Denis Ryan was stopped from investigating allegations of child sexual abuse by a Catholic priest, Victoria Police has admitted a conspiracy to cover up the crimes went right to the top.

Mr Ryan detailed to the Royal Commission into Institutional Responses to Child Sexual Abuse how his attempt to investigate allegations against Monsignor John Day in the 1970s was thwarted by what he describes as a "Catholic mafia" within the force.

"The common law of the police force was not to charge a priest, short of murder," Mr Ryan, 83, said.

"The Catholics looked after the Catholics and the Masons looked after the Masons."

In 1971 while stationed in Mildura, Mr Ryan learnt of numerous allegations against the assistant priest of the parish, Monsignor Day.

"It was like stepping stones. It wasn't difficult," he told the inquiry.

Yet Mr Ryan was thrown off the case by his seniors who he described as staunch Catholics; in particular, Detective Sergeant Jim Barritt, who was best friends with Monsignor Day, and Swan Hill superintendent and chief investigator Jack O'Connor.

He also named Superintendent Jack Partland and Inspector Alby Irwin as being part of efforts to thwart the investigation.

Mr Ryan said he wrote to Ballarat Bishop Ronald Mulkearns about Monsignor Day, and was threatened outside Mildura Police Station by Mildura parish priest Father Peter Taffe.

Bishop Mulkearns had been called to appear before the commission, but was excused due to his poor health.

Ryan showed 'relentless pursuit of justice'

Despite Mr Ryan's efforts, Monsignor Day was never charged but was eventually moved from the parish and banned from working with children.

Former Victoria Police commissioner Mick Miller (L) and current chief Graham Ashton outside the hearing. ( AAP: Tracey Nearmy )

Giving evidence after Mr Ryan, former chief commissioner Mick Miller told the hearing his immediate predecessor, Reg Jackson, was the key player in the police cover-up of the abuse.

"It couldn't have operated as it did without his knowledge and consent," he said.

Mr Miller said Mr Ryan was owed an apology and compensation.

"My admiration for him, for his relentless pursuit of justice the victims of Monsignor Day's paedophilia is boundless," he told the inquiry.

"The driving force behind the crusade was a desire to achieve justice for the victims of a hypocritical paedophile priest."

Acknowledgement 'took a bloody long time'

Outside court, current police Commissioner Graham Ashton said he accepted the evidence given by both men and he would be making an apology to Mr Ryan.

Mr Ryan thanked Mr Miller, calling him a "very courageous man" for supporting him.

"It's most satisfying. I hate swearing, but it took a bloody long time" he said.

"If there is compensation I would be delighted, but it certainly wasn't done for compensation."

Commissioner Ashton apologised to Monsignor Day's victims.

"It's been all about saying sorry, trying to move forward and trying to make sure we don't do these things in the future," he said.

Cardinal Pell 'yelled' at victim reporting abuse

Ahead of Cardinal George Pell's appearance before the commission next week, further light was shed on what he apparently knew about priests molesting children during his time in the Ballarat diocese.

A survivor, referred to as BWF, told the inquiry that when he was 14 years old he sought help from Father Pell after discovering his brother was being abused by Christian Brother Edward Dowlan at St Patrick's College in Ballarat.

A convicted paedophile, Dowlan has since changed his name to Ted Bales and is in jail for abusing young boys.

BWF said one day after school in 1973 he went to the presbytery at St Patricks Cathedral.

"I was angry about the situation and frightened and nervous and anxious about it," he said.

"I just blurted out to Pell that Brother Dowlan had beaten and molested [his brother] BWG and demanded to know what Pell going to do about it.

"Pell became angry and yelled at me 'young man, how dare you knock on this door and make demands'."

BWF told the inquiry he had gone to Father Pell as he was well known as an influential priest and was revered by children.

"The reason I went to him was because I wasn't being heard at school," he said.

Pell was not living in presbytery, lawyer says

Cardinal Pell has consistently denied that he was aware priests were sexually abusing children during his time at the Ballarat diocese between the 60s and 80s.

Under cross-examination, counsel for Cardinal Pell, Sam Duggan, said BWF was making up a story.

"Father Pell was not living in the presbytery on Sturt and Dawson Street in 1973 and had no reason to be there," he suggested.

He said he was living at St Alipius presbytery a couple of kilometres away.

"I suggest to you that you are making this story up about visiting Father Pell at the Cathedral presbytery and you never confronted him there?" Mr Duggan said.

BWF replied: "That's your opinion."

The hearings continue.