For the past 30 years John Hume has been the chief conceptualiser and steely presence behind nationalist demands for equality of treatment and a recognition of their political aspirations in Northern Ireland.
During that time he has annoyed a succession of governments in this State with his demands and initiatives. He has appeared to unionists as their most dangerous enemy. And he has infuriated British governments by enlisting opinion in the US and in Europe in favour of comprehensive change.
John Hume does not operate happily within systems. He is not a committee man. But his vision, determination and effectiveness in lobbying the main centres of power have been nothing short of spectacular.
Although he leads what is only the second-largest party in Northern Ireland, he has effectively managed to dictate the thrust of Irish and British government policy for the best part of 20 years. While unionist parties resisted change by relying on their traditional response of saying "No", John Hume was at the centre of a series of political initiatives. And, in a climate of reform, he wasn't averse to using a nationalist "veto" to prevent the re-emergence of old-style unionist control.
In the Republic his status as leader of nationalist opinion in the North made him politically untouchable. His unequivocal stand against violence and in favour of an accommodation with unionists bestowed on him a form of political saintliness. He now enjoys near-open access to the White House in Washington. And his influence in the European Parliament is considerable.
You don't dominate the political horizon in that fashion without making enemies and attracting criticism. And the leader of the SDLP is no exception. Even within his own party, Mr Hume has been increasingly faulted for a lack of consultation on policy initiatives and directions, particularly where Sinn Fein is concerned. Unionists describe him as arrogant, self-centred and rude. And government ministers, used to controlling and dictating events, find his independence a trial.
But if courageous leadership and results are the measure of a politician, John Hume has nothing to apologise for. The new, inclusive political settlement that has emerged is largely his creation. And aborted and failed attempts were necessary signposts that led up to this point.
It has been a long road since the Derry politician was first elected to Stormont in 1969, having risen to prominence through the civil rights campaign. The old, abstentionist, Nationalist Party was dying. And Mr Hume joined with Gerry Fitt, Austin Currie, the late Paddy Devlin and others in forming the Social Democratic and Labour Party in 1970.
Following the fall of Stormont and the imposition of direct rule from Westminster, he and his colleagues lobbied the British and Irish governments for a new departure. When it happened at Sunningdale in 1973, Mr Hume became a minister within the first Northern Ireland power-sharing executive, headed by the late Brian Faulkner.
As part of the Sunndingdale deal, in return for agreement on an embryonic Council of Ireland, the Irish government provided an assurance that the status of Northern Ireland would only change with the consent of a majority of the people there.
A split in the unionist party, followed by a civil disobedience campaign, the loyalist workers' strike and continuing Provisional IRA violence brought about the collapse of the power-sharing executive in 1974. Harold Wilson and the British Labour government had failed to mobilise the Northern Ireland security forces in defence of the executive. Direct rule was reimposed from London, and British ministers went back to the drawing board.
As Provisional IRA violence escalated and loyalist gangs engaged in tit-for-tat killings, British governments concentrated on finding a security-based solution - to no avail. Through it all, the SDLP held the line on the primacy of democratic politics and rejected the use of force.
As stalemate continued between the two communities in Northern Ireland, John Hume sought, and secured, election to the European Parliament in 1979. In the same year he succeeded Gerry Fitt as leader of the SDLP. It was to mark the beginning of several key initiatives.
The brief thaw in Anglo-Irish relations leading to a Dublin Castle summit between Charlie Haughey and Margaret Thatcher in 1980 didn't last. Talk of developing the "totality of relations" between these islands evaporated as unionists rejected the notion of power-sharing; the H-Block hunger strikes convulsed Irish politics, and Mr Haughey criticised Britain's involvement in the Falklands war.
Meanwhile, Mr Hume was canvassing support for nationalist aspirations within Europe. But the main focus of his attention was the US, where the Provisional IRA and Sinn Fein had enjoyed traditional support among Irish-Americans for their physical-force methods.
Cutting the supply of money and arms became a priority. Supplementing the Irish government's diplomatic offensive, Mr Hume began lobbying at the top in Washington. Soon powerful Irish friends emerged on Capitol Hill.
And the "four horsemen", Ted Kennedy, "Tip" O'Neill, Pat Moynihan and Hugh Carey, were not averse to advising the Irish government on diplomatic representation and policy direction when Mr Hume spoke.
Within a few years the power and influence of Noraid and the Provisionals was broken as the US courts sought disclosure of their records. Democratic methods were in the ascendant. Mr Hume's American connections, particularly with the powerful Kennedy clan, became the source of his greatest influence.
In the South pressure from Mr Hume led to the Fine Gael-Labour coalition government setting up the New Ireland Forum in 1983. Nationalist parties considered the situation and provided a report on the available political options, including the traditional, distant aspiration to Irish unity. But all were rejected by Mrs Thatcher in her notorious response: "Out . . . Out . . . Out."
Subsequently, the withdrawal of the SDLP led to the collapse of the Northern Ireland Assembly. And, by 1985, Mrs Thatcher had been encouraged by Garret FitzGerald, with John Hume and powerful US opinion in the wings, to sign the Anglo-Irish Agreement at Hillsborough.
It was a kind of Sunningdale Mark II. For the first time an Irish government was to be granted formal consultative rights in relation to Northern Ireland through a jointly-chaired Inter-Governmental Conference. Pending the devolution of powers to a local parliament or convention, Dublin could make proposals on the administration of justice, on cross-Border co-operation and on security and related matters.
It was a classic carrot-and-stick approach. Dublin's influence would diminish if unionists and nationalists operated the political structures. Otherwise, the interests of nationalists would be represented by Irish ministers.
There was a final twist. A secretariat was established in Belfast, staffed by British and Irish civil servants, to ensure the smooth working of the Inter-Governmental Conference.
In return for these changes, the Irish government accepted the concept of "consent", that the constitutional position of Northern Ireland within the United Kingdom would not change unless a majority so decided.
On the other hand, the British government agreed to legislate for a united Ireland if that became the wish of the majority.
The agreement, designed to bring about "peace, stability and prosperity", generated an explosion of unionist and loyalist violence. It was rejected by republicans as partitionist. And the "consent" clause was declared to be unconstitutional by Charles Haughey, who was then in opposition.
An attempt by unionists to have the agreement revoked by the British government, through a campaign of civil disobedience, failed. Later, in government, Mr Haughey worked the agreement, but spoke of negotiating a treaty that would transcend it. A review of its contents in 1989 expanded ministerial, cross-Border co-operation and led to the establishment of an Irish-British Interparliamentary Body.
The departure which led to the current phase of negotiations was again initiated by John Hume, when he opened discussions with Gerry Adams of Sinn Fein.
The SDLP leader had become convinced that an inclusive, rather than an exclusive, approach was required if a lasting political solution was to be achieved in Northern Ireland. The marginalisation of Sinn Fein and loyalist politicians had failed to provide the centre with a new dynamic. The gunmen and the marginalised had to be involved if a deal was to hold.
It was the SDLP leader's idea that negotiations should take place in three strands: one dealing with internal Northern Ireland matters; one covering North-South arrangements; and the third an Irish-British accommodation. Again, there were powerful echoes of Sunningdale, but in a new political configuration.
Under Mr Hume's prompting, the Northern Secretary, Peter Brooke, undertook an extended "talks about talks" process with the Northern Ireland parties. In the course of those discussions it was stated publicly that Britain had "no selfish interest" in Northern Ireland. It was a covert signal to the IRA. And Sinn Fein edged closer to the negotiating table.
Using US influence, Mr Hume brought pressure to bear on both the British government and the Provisionals. The Hume-Adams dialogue took on real political significance as the IRA grudgingly acknowledged it could not win a war against the British army in Northern Ireland.
Progress was painfully slow. But when Mr Hume convinced Albert Reynolds and Dick Spring there was a real chance of securing an IRA ceasefire, in 1992, it opened the way for the Downing Street Declaration of 1993. And it provided a framework, embracing parity of esteem, within which Northern society could grow towards compromise and the development of a middle ground.
In it, John Major spoke of "encouraging and facilitating an agreement, based on the rights and identities of both traditions . . . which may take the form of agreed structures for the island as a whole, including a united Ireland achieved by peaceful means".
Albert Reynolds embraced the concept of consent on behalf of Fianna Fail. And the Government offered to express the claims of Articles 2 and 3 "in a more balanced way". At Mr Hume's prompting, it also secured Mr Major's agreement that any political settlement would be put to the electorate on both sides of the Border in simultaneous referendums.
Ian Paisley and the DUP condemned the document, but the Ulster Unionists remained neutral. Gerry Adams and Martin McGuinness were encouraged to take the democratic road, even at a cost to the SDLP of lost electoral support. But, as the IRA campaign continued, John Hume was heavily criticised for putting his party at risk and for flirting with terrorism.
Within a year, however, the IRA and loyalist paramilitaries had declared ceasefires and their political representatives were knocking at the door to negotiations.
Unionist demands for arms decommissioning and Mr Major's dependence on their voting support at Westminster kept that door closed until US pressure and the involvement of George Mitchell provided the mechanisms to surmount the roadblock.
There were to be further difficulties and delays as the unionists sought and secured an electoral process; the IRA ceasefire broke down and the two governments disagreed on procedures and objectives.
John Bruton and Dick Spring finally agreed a Joint Framework Document with a fatally weakened British government in February 1995. Through it all, Mr Hume cultivated his US contacts, maintained contact with Gerry Adams, and kept faith with his blueprint for a settlement.
The election of Tony Blair as Prime Minister in 1997 gave a new impetus to the talks, which was added to by Bertie Ahern's selection as Taoiseach. Within months, they had set a deadline for a renewal of the IRA ceasefire, as a condition for Sinn Fein's admission to the talks. It was met. The Government-modified Hume-Adams initiative was back on the rails.
During the past six months, there have been alarums and excursions, demands and recriminations, and plenty of hope and despair as the parties, driven onwards by the two governments and facilitated by Senator Mitchell, inched towards accommodation.
Some months ago, the present exercise was described as "Sunningdale for slow learners" by Seamus Mallon. It was a sharp jibe at those unionists who had consistently rejected change and at militant republicans who thought a solution lay in physical force.
Much has changed since Sunningdale. In 25 years the economy of the Republic has powered ahead, and living standards in the South now outstrip those of the North. Reform of the RUC, fair employment legislation, housing and welfare changes have been reflected in a growing confidence within the nationalist community. Membership of the European Union has encouraged understanding and co-operation between the two governments. And the prospect of economic growth, based on cross-Border co-operation, is attractive to hard-headed businessmen.
But acceptance of new relationships and equality of esteem between the two communities in Northern Ireland will not come easily or in the short term. It will require courage and commitment from politicians, churchmen and civic leaders.
In that regard, John Hume is a towering example for nationalists of the committed democrat who has taken risks for peace. He has used the political system - even placed his own party at risk to Sinn Fein - as an alternative to sterile, destructive violence. More than any single party leader in this process, he has designed the architecture around which a settlement has been reached.