Before Bill Clinton, the US President, who was instrumental in the Irish peace process, there was Senator Ted Kennedy.
Senator Ted Kennedy helped Sinn Féin's Gerry Adams secure a US visa
While it was the president who granted the Sinn Féin leader Gerry Adams a critical visa to the US in the run-up to the IRA ceasefire of 1994, it was the senator who helped persuade the president.
"Ted Kennedy was the key that unlocked the Clinton White House door over and over again. That's not just once, but many times," said Eamonn Mallie, co-author of The Fight for Peace.
Indeed, the Massachusetts Senator was himself not keen on assisting Sinn Féin. As a long-time supporter and friend of John Hume, the nationalist leader who opposed violence, Senator Kennedy had no time for violent republicanism.
It was only at Mr Hume's insistence that the senator was convinced to lobby the Clinton White House.
The visa was critical to the IRA ceasefire because Sinn Féin's peace strategy involved not only persuading its Irish American supporters of the merits of the ceasefire, but also of showing grassroots republicans that peace would bring political influence and international support.
Despite their differences, the senator went on to publicly defend Sinn Féin when he believed it necessary and Mr Adams paid tribute to the senator's contribution to peace as "exceptional" and "significant."
Mr Hume called Senator Kennedy "a great friend of Ireland." For years, the two were in regular contact and met whenever the SDLP leader was in Washington.
Senator Kennedy's relationship with Britain was not so warm, particularly in the early days of the Troubles, when he infuriated London - and unionist politicians - by backing the Troops Out movement in 1971.
Mr Kennedy was a long-time supporter and friend of John Hume
The young senator likened arguments against troop withdrawal to those he had heard about American soldiers in Vietnam. What's more, he refused to accept his views as interference in an internal UK dispute, always insisting it was an international matter.
Over the course of his senatorial career, he challenged British policy and also took up some controversial cases, involving allegations of collusion between loyalist paramilitaries and British intelligence.
He also supported the families of the victims of Bloody Sunday, whose relatives were shot dead by the British Army in 1972.
As one of four power-brokers on Capitol Hill dubbed the Four Horsemen, Senator Kennedy was a thorn in the side of the British, who used his influence to build support across Washington for his point of view.
He helped to widen the vision of Irish Americans to the realities of Northern Ireland
David Ford Alliance Party leader
When Prime Minister John Major, who had secretly authorised private talks with the IRA, refused to speak to its political allies in Sinn Féin post-ceasefire, Senator Kennedy stepped up the pressure for talks with a very public attack on British policy.
He said: "So many Americans have difficulty in understanding...how a Prime Minister can be talking to the representatives of the IRA when they are involved in violence, as Mr Major was, and then to have a whole period of 17 months when there is no violence and refusal to engage in conversation."
Those remarks certainly did not sit well with the "special relationship" that London liked to display with Washington.
His close relationship with Irish nationalists drew unionist suspicion and ridicule.
But with the peace process came a shift in relations and Senator Kennedy was applauded when he took up the case of Robert McCartney, a Catholic believed to have been murdered by members of the IRA in 2005.
Mr Kennedy snubbed Gerry Adams in 2005, instead meeting the McCartney sisters
Senator Kennedy refused to meet Gerry Adams in Washington in protest, instead meeting the dead man's sisters. That snub shook Sinn Féin and certainly added to the pressure on the party to encourage co-operation with the police.
At St Patrick's Day celebrations in Washington, Senator Kennedy played a key role and unionist politicians soon recognised the merits of having him on side.
Senator Kennedy came to Stormont in 2007 to personally witness Ian Paisley, the DUP leader, become First Minister alongside Sinn Fein's Martin McGuinness as Deputy First Minister.
However, there was sharp criticism when London awarded him an honorary knighthood in 2009.
A number of DUP politicians expressed their anger publicly.
Other unionists, including the Ulster Unionist leader Sir Reg Empey, recognised the distance the senator had travelled when he accepted the honour.
But even the DUP, once led by firebrand Ian Paisley, found kind words for him in death, acknowledging the distance he himself had travelled.
DUP assembly member Peter Weir said: "Latterly, he came to recognise the validity of the Unionist argument and the reality of partition."
Another politician, the Alliance leader David Ford, summed up his contribution: "He helped to widen the vision of Irish Americans to the realities of Northern Ireland and will be remembered for the part he played in our peace process.
Martina Purdy looks back at Senator Ted Kennedy's involvement in the Northern Ireland peace process
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