A report by the North's Police Ombudsman, due to be published next month, is expected to cause embarrassment to the British government, the Catholic Church and the police.
The Ombudsman, Nuala O'Loan, has been investigating allegations that after nine people died in the Claudy bombing in1972, senior figures from the Catholic Church, the British government and the RUC conspired to move one of the potential suspects, a Catholic priest, from the jurisdiction.
Three car bombs went off without warning and killed nine local people in July 1972.
Five of the victims were Catholics, four were Protestants.
Although nobody has ever been charged with the crime, the IRA in south Derry is blamed.
It was said at the time that because of a broken telephone exchange in Dungiven, the bombers failed to relay a warning.
Four years ago some of those injured in the bombs received a letter alleging that a Catholic priest had played in a crucial role in the bombings.
The PSNI revisited the file and the Police Ombudsman also became involved.
Next month she will publish her report.
RTÉ News understands that Nuala O'Loan may conclude that the Catholic Church, the then RUC and the British government did indeed conspire to move a potential suspect from the jurisdiction.
That man was Fr James Chesney, who was a Catholic curate in the nearby village of Desertmartin at the time. He later moved to the Republic and died there in 1980.
Mrs O'Loan has refused to comment on her report prior to its publication.