Valentine, 78, would "go ballistic" about staff who asked why he was still working in such a senior position after facing child sex charges in 1987 and 1988, said Max Morrissey, who was a Hunter child protection consultant reporting to Valentine.

"Everybody knew about Frank," said Mr Morrissey, after Valentine was last week found guilty of sexually abusing six children in NSW Government-run facilities.

"He rang me one night and said how terrible it was that people were talking about him and saying he sexually abused children. He said he was going to get them all and have them put in jail. He would go around saying people were making false allegations against him and about not being guilty, so a lot of people knew about Valentine," said Mr Morrissey, a Charles Sturt University academic.

"There's been a lot of attention on churches and child sexual abuse but there are aspects of Valentine's history that make it perhaps more dreadful than many other serial predators," he said. 

The only surprise about Valentine's conviction for serious child sex offences was that it took so long, Mr Morrissey said.

But it was almost inevitable after women told the Royal Commission into Institutional Responses to Child Sexual Abuse they had been sexually abused by Valentine and others at a government-run facility in the early 1970s.

Valentine denied the allegations and said the women must have confused him for other child sex offenders who worked at the school. He lost an attempt to have his identity suppressed.

The royal commission heard evidence from the Department of Family and Community Services showing alarm bells were ringing about Valentine from at least as early as 1973.

The then Public Service Board in 1973 "had serious concerns about whether Mr Valentine should continue to hold a senior position in the department", documents showed.

The concerns followed sexual and physical allegations made against him during his two-year stint a government facility between 1971 and 1973.

While it could not substantiate the allegations, the board issued him with a warning after finding he failed to respond to serious sexual and physical allegations made by teenage girls against other staff at the institution.  

The board's concerns about Valentine weren't enough to stop him from being transferred to another government residential facility in 1973, and later to Kurri Kurri's Yawarra Training School for troubled teenage boys, where he allegedly sexually abused a 15-year-old in 1978.

Valentine was Hunter operations manager in 1986 when he was charged with raping a ward of the state, aged 11, who he'd taken under his wing while a community program officer in the Riverina region three years earlier. It was against all department rules, but a jury accepted the word of a very senior department employee over a troubled powerless child and Valentine was acquitted of the offences.

Valentine was charged with more offences in 1988, including sexually abusing a teenager at Yawarra in 1978. But the charges were dismissed after the alleged victim, 25, committed suicide two days before he was expected to give evidence at the trial. A second alleged victim chose not to go ahead after the man's death.

Valentine returned to his senior Hunter position after the charges, said three former department employees, including Mr Morrissey.

"I can't understand it," Mr Morrissey said.

"I'm guessing it would have gone to senior people in the department who would have taken a very legalistic view and said 'Not proved, not guilty, he can return to work'," he said.

"I certainly think he was protected in the early days."

The department would not comment on the case but three former department employees said they believed Valentine had the support of the late Percival Mayhew, a former senior department employee, who was also the subject of serious child sex allegations raised with the royal commission.  

NSW District Court Judge Nicole Noman last week found Valentine guilty of 20 historical child sex offences against six victims, including rape, buggery and indecent assault. He was bailed before his sentence on May 24.

The Department of Family and Community Services on Friday declined to provide details of Valentine's history in the Hunter region, including when he worked at Yawarra or whether he worked at Worimi Shelter at Broadmeadow, which operated from 1966 to 2006 as a reception facility for children facing court.

Mr Morrissey said he was not surprised to read that police could lay more charges against Valentine, who lives with wife Maris in Queensland. Mrs Valentine also worked for the department in the Hunter.

Mr Morrissey and another former Yawarra employee who worked with Valentine said they were contacted by police about Valentine over the years, including in the 1990s, but little came of it.

It was not until the royal commission that allegations about Valentine were formally raised.

The former ward of the state who was devastated after a jury believed Valentine rather than him in 1987 told the royal commission he wanted to know "how this man was allowed to continue his career with young people" after leaving a trail of child sex allegations behind him. 

Mr Morrissey and other former department employees say it is the unanswered question as Valentine faces a jail sentence for his crimes.

Do you know more? Email jmccarthy@fairfaxmedia.com.au