MacArthur is currently the second-longest-serving prisoner in the Irish prison system for the brutal killing of nurse Bridie Gargan in the Phoenix Park 25 years ago today, but he was never pursued for a second murder.

Days after MacArthur's crazed attack on Gargan, he shot dead farmer Donal Dunne with Dunne's own gun near his home in Edenderry, Co Offaly.

After a remarkable trial that lasted just five minutes, he was sentenced to life imprisonment, which usually means up to 15 years in Ireland, for the murder of Gargan in January 1983. There was public outrage after it emerged that he would not face trial for the murder of Dunne.

The Sunday Tribune has learned that MacArthur has told a public servant who has had direct dealings with him and a number of his fellow inmates that the state told him that he must leave the country immediately if he is ever released.

It is understood that MacArthur was told about his possible exile, most likely by an official from the Department of Justice, at the time of his trial for the murder of Gargan in January 1983.

After one of the biggest murder hunts in the history of the state, a bizarre sequence of events led investigating gardai to arrest MacArthur in the Dalkey home of the then attorney general Paddy Connolly, where Connolly had innocently allowed his old friend MacArthur stay.

In 2003, the Parole Board recommended MacArthur be put on a temporary release programme which would eventually lead to his release, and he has been out on a number of occasions since then.

MacArthur's current solicitor, James MacGuill, told the Tribune this weekend that he had not heard of the state's plea to his client, whereby he would leave Ireland if he was released, but "that is not to say that it did not happen". He has had a number of solicitors since his sentencing in 1983.

It has also emerged that MacArthur has told some of his fellow inmates that he had been willed a property in South Africa.

Speaking to the Sunday Tribune this weekend, Gordon Holmes, Limerick-based solicitor and chairman of the parole board, said: "I am not aware of any deal like that. We would not take a prisoner leaving the country into account when determining if they were to get parole.

"Whether a person is leaving the country or not does not guarantee that they would not come back into the country afterwards."