It also features a cry for help from a police officer and a principal for agencies other than CYFs to step up - just as Children's Commissioner Russell Wills is currently pushing for the responsibility for at-risk children to be spread wider.
"It is not the responsibility of Child, Youth and Family alone," Dr Wills told the Herald. "Schools, families, communities, charities, businesses, health providers and other government agencies have the power to change the lives and outcomes for these children. These are our children, too."
The file was released to the boy's mother under the Official Information Act and Privacy Act, then given to the Herald after she died this year. It shows 11 formal reports of concern about the boy's welfare were lodged with CYF between June 2001 and July last year. In that time, 10 legal orders were issued to help CYF manage Benjamin's care.
Over those years, the notes recorded:
The boy suffered head injuries as a toddler when dropped because his mother was too drunk to hold him.
He went missing overnight when aged 4 and was found in a stream "lucky to be alive", according to the police.
He once arrived at school with black eyes, bruising to his body and burn marks on his stomach.
He was seen in a car with his hands tied with a dressing gown cord behind his back.
CYF's involvement with Benjamin ended in 2008, when it was satisfied he had been safe in the two years he had been in his father's care. It was unaware until late 2010 that his father had returned the boy to his mother's care.
The CYF file recorded serious concerns about the mother's drinking and also her complaints that her partner, who was paid by her parents to be her caregiver, had hit and raped her.
The social worker's description of Benjamin as a "cash cow" for his caregivers came after a visit to the boy's North Island home in July 2014.
Concerns had been raised over violence between his mother and her boyfriend.
Benjamin was found locked in an unfurnished room, sitting on a wooden floor with a plastic toy. His bed had no linen, his nappy was wet and the room was unheated, while his mother was drunk in a neighbouring room warmed by a fire.
The incident came a year after the principal of the school Benjamin attended at the time sent a call for help to the Ministry of Education, the Accident Compensation Corporation and CYF. She emailed CYF about "large setbacks" because of staff changes at a range of agencies and delays in accessing support.
A police officer copied in on the email replied: "Despite efforts from a few, we are now faced with this situation - this unenviable situation - that is going to cause someone some injury or harm that earlier intervention by the appropriate person/agency could well have prevented."
Benjamin's health needs had to be addressed and "someone needs to put their hand up and accept responsibility", the police officer wrote.
Benjamin's mother's lawyers - before her death - raised concern about her former partner and paid caregiver being granted custody of the boy.
She died last February of liver failure. Benjamin was returned to his father's custody in July - almost a year after being placed in the care of his mother's boyfriend.
Benjamin's father said he had not been told for months that his son had been taken from his mother. Had he known, he would have resumed care earlier.
• Benjamin's name has been changed for legal reasons.
CYF opts to stay silent on case
Child, Youth and Family declined to comment on the case for fear it could lead to identification of Benjamin*.
CYF regional manager John Langley said: "Child, Youth and Family's role is to promote the best interests of the child. The Family Court ultimately makes decisions around custody of a child, taking into consideration the views of those involved.
"This includes Child, Youth and Family social workers, parents, legal guardians, the Counsel for Child, and any other parties the court wants involved."
He said it was "not appropriate for details of this case to play out in the public arena, especially since, sadly, [Benjamin's mother] has now passed away and the matter relates to a vulnerable child".
"We must protect the privacy of all the people involved in this matter, including [the mother], even if it means not being able to explain our own actions in the face of claims that do not accord with the facts we hold."
