Mr David Trimble came to Dublin especially to be on The Late Late Show last night, the first UUP leader to visit RTE.
His appearance on the show, where he was interviewed by Pat Kenny, came after renewed requests from the programme's researchers since Christmas.
A Late Late Show researcher, Mr Will Hanafin, said they had contacted Mr Trimble at various times as he was an "A list" guest and they were eager to get him on the show.
A few weeks ago Mr Gerry Adams appeared on the show. After that, researchers made a fresh request to Mr Trimble to appear. Factors which helped him change his mind were the suspension of the Northern Ireland Assembly; audience reaction to the interview with Mr Adams; and two biographies which are coming out about him.
"I put it to him again and asked him why not come on the show. He initially agreed to appear on March 10th, but that didn't work out. The earliest date after that due to certain factors like St Patrick's Day and the UUP conference was March 31st," Mr Hanafin said.
He contacted Mr Trimble's office on Monday, went to Stormont on Tuesday and had a pre-interview with the UUP leader. "Mr Trimble was very eager to do it. He was very positive and very helpful," he said. The plan was for Mr Trimble to arrive 50 minutes before he was due to go on the show and to give a 35-minute interview in part four.