The funeral will take place later of Fr Alec Reid, who was a key figure in the Northern Ireland peace process.
Hundreds of mourners are expected at Clonard Monastery in west Belfast, his base for four decades.
Paying tribute to Fr Reid, Sinn Féin President Gerry Adams described Clonard as "the cradle of the peace process".
Fr Reid secretly acted as a conduit between the republican movement and the SDLP, and years later was a witness to the IRA destroying its weapons.
He was pictured in one of the starkest images of the Troubles in 1988, when he was photographed praying over the bodies of Army corporals Derek Wood and David Howes.
They had been dragged from their car, beaten and shot by the IRA after inadvertently driving into a republican funeral cortege.
In recent years, the Redemptorist priest was involved in talks with Basque nationalists seeking independence from Spain.