PHILADELPHIA - Senator George Mitchell is usually a careful speaker when it comes to Ireland.

By virtue of his role as chief mediator in the talks that led to the historic Good Friday Agreement, Mitchell has to watch his words, lest he retroactively offend any of the parties he once negotiated with.

Indeed, he tells a wonderful story about his first day in charge of the talks when the late David Ervine, head of the Progressive Unionist Party, told him that every one in the room would travel 100 miles to be insulted, just so they could feel sorry for themselves.

Mitchell told that one at the American Ireland Fund luncheon in Philadelphia on Friday, which paid tribute to the 10th anniversary of the agreement. He was the guest of honor at the event which was attended by, among others, MSNBC personality and Hardball presenter Chris Matthews, who emceed the event.

Incidentally, Matthews hinted strongly that he would run for the Senate in 2010 from his home state of Pennsylvania, a sure case of fox turning gamekeeper.

Mitchell is a poster boy for discreet, a man so trusted that Major League Baseball, the International Olympic Committee, Northern Ireland advocates and Middle East peacemakers have all enlisted him at different times in their search for solutions to their problems.

On Friday, however, he was more open and forthcoming than I have ever heard him about the personal side of George Mitchell. He spoke very movingly about his father, George John, who was adopted soon after the family came over from Ireland, and he spoke about what it would mean to his own young family if there were long-term peace in Ireland.

Last August Mitchell, through his law firm, announced that he was suffering from prostate cancer. Perhaps grappling with that disease - which he seems to be doing successfully - has made him a little more open to discuss the hard times his family encountered after they came to America.

The Mitchells are really the Kilroys, probably from Cork, or that may just be where the boat left from. Despite his best efforts Mitchell has been unable to trace his family, finally admitting that they were likely lost in the mists of time, like so many dirt-poor Famine era emigrants.

Soon after they emigrated George's father, then a young child, was put in an orphanage. It is not clear what happened to his parents.

In the fashion of the day, as Mitchell recounted, the orphaned kids were brought to the local church in Maine and lined up at the altar rail where parishioners could literally walk them home and adopt them there and then. This is how George Mitchell's father came to bear that last name as an elderly couple gave him a home.

In turn his father married Mary Saad, who was born in Lebanon. Times were hard. His father was a janitor at a local college. Yet the son grew up to be a judge, a senator and a peacemaker, and a nominee for the Nobel Peace Prize in 2000.

Mitchell spent five years in Belfast seeking to negotiate the peace accords. By any measure it was an astounding feat, one he is reluctant to take credit for.

Ruefully he tells the story of so many locals who came up to thank him for trying, but usually they added quietly that they did not think he had a chance of succeeding.

I was of that mindset myself to an extent. Before Mitchell went to Ireland as President Clinton's emissary I met him at his midtown New York law office. At the time the peace was very fragile and the notion of a Good Friday or St. Andrew's Agreement was merely a pipedream. I remember feeling sorry for this man, undertaking what looked like a Herculean task.

Impossible or not he was up for it. He drove the process forward until the final weekend of Good Friday in 1998, and then delivered a spectacular agreement that has entered the history books as an example of conflict resolution.

Mitchell finished his talk to the American Ireland Fund on an upbeat note. For years he has stated it was his ambition to take his young son to Ireland to sit in the visitor's chamber of the Northern Ireland Assembly and watch democracy take place.

Until the recent power-sharing government he felt he could never take his son on that trip, believing that the peace was not yet secured. On Friday he told the guests he was ready to go with his son.

It was a dramatic moment that earned him a standing ovation. It was no less than he deserved.