Highly sensitive documents on the Kincora scandal will remain locked away in Northern Ireland's official archive for decades to come.
At least 19 files directly related to the notorious east Belfast care home are "closed" to the public.
In one case, the order remains in place until 2085 at the earliest. Around a dozen more of the files are closed - either fully or partially - until the mid-2060s and beyond.
Others which were scheduled to be declassified in recent years remain at least partly shut.
The department responsible for the records said they contained "sensitive personal data" and could not be opened in order to protect victims' personal details and to comply with data protection legislation.
However, Ulster Unionist MLA Mike Nesbitt said the secrecy would only lead to more questions.
"The suspicion is they are hiding something. Is that legitimate? We can't make that judgment when we don't know what is in there," he said.
The Kincora scandal shocked Northern Ireland when it emerged in 1980.
At least 29 boys were sexually abused at the care home.
Three senior staff members - William McGrath, Joseph Mains and William Semple - were jailed in 1981 for the abuse.
However, allegations have persisted of a cover-up by MI5, which was rumoured to be protecting high-ranking paedophiles in the military, Civil Service and politics. It was claimed the RUC had been informed of the abuse years earlier, but failed to act.
A "private inquiry" was set up in 1982 by the then Secretary of State Jim Prior to investigate the scandal, but it fell apart after three members resigned, claiming the RUC hadn't carried out an effective probe.
Mr Prior established another inquiry under Judge William Hughes, but most of his recommendations were about the operation of children's homes and care for young people generally.
In 2017 retired judge Sir Anthony Hart published a report after a long-running inquiry into historical institutional abuse in Northern Ireland. His report dismissed claims that senior figures were complicit in a paedophile ring, and that the UK security services knew what was going on.
However, questions have been raised over the inaccessibility of many official papers. The papers are held by the Public Record Office of Northern Ireland (PRONI), the region's official archive.
Files on Kincora were conspicuously absent when government papers from 1982 were declassified in December 2012.
A list of closed files held by PRONI show at least 19 are directly linked to Kincora.
Four, which were listed for review in 2013, remain closed. Three more are listed for review between 2020 and 2026. The other 12 have review dates ranging from 2067 to 2085, meaning they are not due to be declassified until these dates at the earliest.
In some cases part of the file has been made public, with its other contents redacted, or blanked out.
The file closed until 2085 contains "transcripts of proceedings of (the) committee of inquiry into children's homes and hostels", and "evidence of witnesses". Two other files, closed until 2080, contain similar material.
Mr Nesbitt said he was "surprised and concerned" by the revelation. He said one option was to open the files to independent scrutiny.
"If you lock away files for that length of time then people will think there is something really serious to hide," he added. "A compromise position might be to allow a senior, respected figure like a retired High Court judge - someone who knows what they are doing - to inspect the files and make a general statement, at least to dispel any suspicion."
Alliance leader Naomi Long said Kincora's victims deserved answers. She said: "This lack of transparency and repeated refusal to open the files relating to this case fuels the perception there was, at best, more knowledge of what was happening at Kincora Boys' Home at the time than has been admitted, and, at worst, Government cover-up of or collusion in the abuse itself.
"These papers need to be released so that abuse can be investigated properly and in a way which will bring truth and justice to the victims and survivors of Kincora."
PRONI falls under the remit of the Department for Communities. A spokesperson said: "The files are closed because they contain sensitive personal data. It is an extended closure period to protect the names and other personal details of victims and to comply with data protection legislation."
On Friday this newspaper reported that confidential Government files on Kincora held in Dublin, that were due to be released this summer, have been kept under wraps yet again.
The secrecy in Belfast has prompted Andrew Lownie, the author of a royal biography on the Mountbattens, to write to Garda Commissioner Drew Harris. He wants access to Irish files on Lord Mountbatten that could shed light on abuse at Kincora.
The Kincora files had been due to be made public under the 20-year disclosure rule but Mr Lownie has been told they "need to be reviewed" before that is likely.