A report into the handling of the Claudy bombing in the north has found the police investigation into a Catholic priest suspected over the attack was stopped after senior officers conspired with the British Government and Church to protect him.
Father James Chesney was transferred to a parish in Co Donegal following secret talks between the then secretary of state William Whitelaw and the head of the Catholic Church in Ireland, Cardinal William Conway.
Nine people, including a young girl, were killed and 30 injured when three car bombs exploded in the quiet Co Derry village in July 1972.
No one has ever been charged.
Father Chesney, who died in 1980 aged 46, has long been suspected as the IRA man who masterminded the atrocity but today's damning report by Northern Ireland Police Ombudsman Al Hutchinson has also revealed the part played by the RUC in the high-level cover-up.
Mr Hutchinson's officers examined diaries belonging to Cardinal Conway which confirmed contact with him and Mr Whitelaw over the priest and correspondence between the RUC.
In December 1972 Mr Whitelaw met Cardinal Conway - the cardinal said he knew the priest was a very bad man and would see what could be done - he mentioned ``the possibility of transferring him to Donegal...''
Father Chesney was transferred across the Irish border in Co Donegal in late 1973 and never ministered again in Northern Ireland.
Mr Hutchinson says there was no evidence that the police had information that could have prevented the attack.
However, he said the RUC's decision to ask the government to resolve the matter with the Church, and then accept the outcome, was wrong.