The home address of the ex-governor of Northern Ireland's high security prison was found in the cell of a dissident republican inmate, the BBC has learned.
Steve Rodford left his job as governor of Maghaberry prison in County Antrim at the weekend. He had been in the post for just five months.
Mr Rodford's car registration details were also found in the inmate's cell.
It is understood he moved out of his County Down home a number of weeks ago and had been staying at a hotel.
BBC Northern Ireland home affairs correspondent Vincent Kearney said: "Mr Rodford's wife was clearly very alarmed by what she viewed as a very serious threat to her security.
"She moved back to England a number of weeks ago and made it clear she no longer wanted to live in Northern Ireland.
"He felt he had no option, other than to step down.
"There has been a general threat against prison officers from dissidents for some time now."
Our correspondent said that Mr Rodford's decision to step down was not just connected to the security threat against him.
"While security is the main factor, it is not the only factor here," he said.
"There have been strong suggestions that Steve Rodford felt he wasn't able to implement the changes he believes were necessary to reform the regime.
"He was appointed after a series of damning reports about the prison, which had been labelled one of the worst and most expensive prisons in the UK.
"When he was appointed by Prisons' Minister Paul Goggins, it was described as a watershed for the Prison Service.
"He arrived from Whitemoor High Security Prison in England with a reputation as a tough but firm governor who wasn't afraid to make tough decisions.
"My understanding was that he quickly became disillusioned with the amount of bureaucracy and red tape in the system and felt he wasn't being given the support and operational independence that he believed he had been promised when he took the job.
"I have been told he expressed these concerns on a number of occasions in recent weeks and even if these potential threats from dissidents hadn't arisen, there was a strong possibility that at some point he may have resigned anyway."
The Prison Service has refused to comment about the security threat against Mr Rodford and said he was moving for "personal and domestic reasons".
Mr Rodford took charge as governor in July, the day before a team of inspectors described Maghaberry as one of the worst and most expensive prisons in the United Kingdom.
Five weeks later, another "vulnerable" prisoner took his own life in the healthcare wing of Maghaberry.
Four health workers were suspended after the death of convicted sex offender John Anthony Deery, whose suicide is now the subject of an investigation by the Prison Ombudsman.
During his short tenure, the governor also ordered the first major search of the jail in more than 10 years.
The search uncovered items which could have been used to make a bomb buried near the jail's perimeter wall.
The operation, which led to all prison visits being cancelled for 48 hours, came just over two weeks after traces of a component used in Semtex explosives were found in the cells of republican prisoners in the jail.
Mr Rodford was appointed as governor, on a secondment basis, following "an accelerated selection process" in the summer.
It followed a review which said a new senior management team - led by a governor from outside Northern Ireland - should be appointed "immediately".
Mr Rodford will take up an appointment at the headquarters of Her Majesty's Prison Service in London early next year.