Charles Haughey (right) became a leading candidate for the job as successor to Irish Prime Minister Jack Lynch in 1979.
Northern Ireland's peace process was the focus of intensive talks with the then British PM Margaret Thatcher.
Mr Haughey was on hand at Dublin Airport in August 1990 to greet Brian Keenan after his release in Beirut.
John Major was another UK leader to meet Mr Haughey as part of the ongoing Northern Ireland peace process.
Soviet President Mikhail Gorbachev met Mr Haughey in a brief summit meeting during a 1989 stopover at Shannon.
Charles Haughey's finances were the focus of the Moriarty Tribunal at Dublin Castle.