Irish police are preparing for their biggest security operation since the visit of Pope John Paul for Queen Elizabeth II's visit next year.
The date of the visit is not known but high-level discussions between British security services, police and the Garda Siochana have taken place.
The Queen's visit has been preliminarily scheduled to mark the completion of the peace process and establishment of the power-sharing assembly at Stormont.
The final leg of the transfer of powers over policing and justice took place in March, and it had been agreed by both governments that following this there would be a historic first visit by the British monarch to mark the completion of the settlement after more than 30 years of Troubles in Northern Ireland.
There has been persistent speculation about the visit but it has only now emerged that gardai have been instructed to prepare for the massive operation to ensure the visit goes off efficiently and peacefully.
The visit will also mark the centenary of the last royal visit to Ireland, that of the Queen's grandfather, King George V, in 1911.
Planning has already begun under Commissioner Fachtna Murphy, whose retirement, originally due in December, is to be deferred so as to ensure continuity of management of the event.
Unlike the Papal visit in September 1979, the visit of a British monarch carries potentially serious security risks from republican terror groups. The dissident republican groups are, however, riven with internal disputes both north and south of the Border.