Christmas with the Clintons: When Bill and Hillary came to Belfast in 1995
Former US President Bill Clinton considers his work in Northern Ireland to be probably his "top foreign policy achievement", according to one of his closest advisors.
The President's White House aide Susan Brophy made the remarks as part of a new documentary on the Clintons' involvement in Northern Ireland.
The BBC Radio Ulster documentary, Christmas with the Clintons, looks back at their 1995 visit and catches up with those who the Clintons met on the day.
"I guarantee you that he considers it probably the top foreign policy achievement of his presidency which says a lot - he was a very successful President," said Ms Brophy who accompanied the President to Northern Ireland.
Bill Clinton developed an interest in Northern Ireland during his time at Oxford University and his administration made the controversial decision to grant Sinn Fein President Gerry Adams a visa to enter the USA in 1994.
A year later Bill Clinton made history by becoming the first sitting US President to visit Northern Ireland when he and First Lady Hillary Clinton touched down at Belfast International Airport on 30 November 1995.
During the trip the President visited a number of areas in Belfast and also visited Londonderry, Armagh and Omagh.
After arriving in Belfast, the Clinton's visited Mackies factory on the Springfield Road where they were introduced by two local primary schoolchildren, David Sterrit and Catherine Hamill.
President Clinton also visited the Shankill Road and the Falls Road where he shook hands with Sinn Fein President Gerry Adams.
Gerry Adams recalls the importance of the visit. "There had to be some signal, particularly on the back of the IRA cessation, that things had changed," he said.
"The actual handshake on the Falls Road was resisted (by the British government) right up to the very hour or two before it occurred."
"My colleague Richard McCauley had a feeling they would block any photograph, so he put a photographer and arranged a video above the shop.
"They brought the President walking down the Falls Road but kept the press back, so thanks to Richard's ingenuity, the moment wasn't wasted."
After the handshake, President Clinton visited an Enterprise Park in east Belfast while Mrs Clinton met a group of women on the Ormeau Road.
The Clintons then made a trip by helicopter to Londonderry. Mark Sheridan who was 10 years old at the time had a special role at the City of Derry airport.
"I was the first person he had to head for to start with. I was wearing a secret service hat which one of the guys who'd been over in one of the previous weeks had given me, and he aimed directly for me when he came out of the helicopter," he said.
"He pointed at the hat and said 'I wear that hat when I'm jogging' and I was amazed at the time that this guy who was on TV every day of the week, and had such an important job in the world, would come over and speak to me."
The evening was rounded off when Bill and Hillary Clinton switched on the Christmas lights outside Belfast City Hall.
The Clintons have continued to be involved with Northern Ireland. Hillary visited in December in her role as US Secretary of State when she said "It's fair to say, that this is a place that keeps drawing me back".
Former UK Prime Minister Tony Blair commented on the commitment of the Clintons to the peace process.
"It was something of a mission all the way through for Bill Clinton during those days. I phoned him virtually at every point of the day and night; he immediately got what the politics was. I don't know how many calls he made to the various leaders but you know they were crucial really," he said.
As Mrs Clinton finishes her term as US Secretary of State, speculation has begun about whether she will run for President in 2016.
Former Republican Congressman, Jim Walsh, who led the congressional delegation to Northern Ireland in 1995 thinks Mrs Clinton may be a contender.
"I have a suspicion, that she harbours an interest, whether she takes a run at it or not I don't know, but I suspect she has an interest," he said.
Jackie Redpath, from the Greater Shankill Partnership believes the Clintons still have a role in Northern Irish politics.
Referring to the violence after the recent flag protests Mr Redpath added: "He's needed back here because there are things he can say about what's going on on the streets at the minute here that people might just listen to.
"I think his future involvement and that of Hillary Clinton is not only likely but is required," he said.
The documentary will be presented by Hillary Clinton's former White House Chief of Staff, Ambassador Melanne Verveer. She continues to work with Mrs Clinton in the State Department.
Mrs Verveer was sworn is as the US Ambassador-at-large for Global Women's Issues in 2009.
The documentary, Christmas with the Clintons, will be broadcast on BBC Radio Ulster and BBC Radio Foyle on Sunday 20 January at 13:30 GMT and repeated on Thursday 24 January at 19:30 GMT. It will also be available on BBC IPlayer Radio.