The late Gerry Fitt's "major achievement" in the late 1960s was to break the convention that Northern Ireland matters could not be brought up at Westminster.
In doing so, he placed the issue of sectarian discrimination in "John Bull's political slum" at the heart of British politics.
This was the verdict of another founder of the Social Democratic and Labour Party, Austin Currie, in a eulogy delivered during requiem Mass for Lord Fitt at Westminster Cathedral yesterday.
"It was an outstanding and crucial achievement which on its own was history-making," he said.
Mr Currie recalled that when Gerry Fitt returned to the North in 1953 after 12 years in the British merchant navy, including dangerous wartime duty on convoys to Russia, he discovered that one-party unionist rule meant there were no jobs or houses for ex-servicemen who happened to be Catholics.
The unionist "stranglehold" on power seemed unbreakable - "but not to Gerry". He identified the "Achilles heel" of unionism in its professed devotion to British standards of fairness and equality, which were not applied to the minority in Northern Ireland.
Although he was the first leader of the SDLP on its foundation in 1970, party discipline did not appeal to him, because "by nature he was an individualist". After the Sunningdale Agreement he led the SDLP to the heart of government, with himself as deputy chief executive.
Although the experiment lasted only six months, "it established for the future the necessary architecture for a lasting agreement".
Gerry Fitt was "a very brave man" who had shown physical courage in his resistance to threats from loyalist and republican extremists, and moral courage in his opposition to IRA violence. He was also "probably the best mob orator of his generation".
Also paying tribute to Lord Fitt, journalist and author Chris Ryder said: "Those of us who were close to him have lost an irreplaceable friend." He was also a friend to the thousands of constituents who came to him, around the clock, looking for help. "No cry for help was ever turned away," he said.
Mr Ryder recalled the story of how the West Belfast MP was once given a seat in the cockpit of a London-Belfast aircraft. While it was in mid-air, he left the cockpit to go to the toilet, only to meet his old adversary, the Rev Ian Paisley, there. To allay his opponent's fears: "Don't worry, I've left it on automatic pilot," he told him.
"He set his compass to the great values of social justice, tolerance and reconciliation, and his course never veered," Mr Ryder added. "He felt betrayed by those who did not share his unambiguous and unequivocal opposition to violence and terrorism."
The chief celebrant at the Mass was Fr Michael Seed, assisted by Frs Christopher Kelly and Malachy Steenson. Danny Boy was played on the violin by Eleanor McEvoy.
The mourners were led by Gerry Fitt's five daughters: Joan, Eileen, Patsy, Betty and Geraldine. The British government was represented by Northern Ireland Security Minister Shaun Woodward.
The President, Mrs McAleese, and the Irish Ambassador were represented by James Carroll, charge d'affaires. Minister of State at the Department of Foreign Affairs Conor Lenihan represented the Government.
Among the other mourners present were SDLP leader Mark Durkan, former SDLP leader John Hume, former UUP leader David Trimble and former Alliance leader Sir Oliver Napier, as well as many other colleagues and associates from a long career, including Ivan Cooper; Paddy O'Hanlon; Dr Joe Hendron; Brendan Halligan and Niall Greene, both of the Irish Labour Party; Kevin McNamara and Kate Hoey MP, of the British Labour Party; Lord Cooke and Dr Steven King of the UUP; former RUC chief constable Sir Ronnie Flanagan; NI Police Board member Tom Kelly; Geoff Martin, adviser to the Commonwealth secretary general; solicitor Denis Maloney; chair of the Irish News James Fitzpatrick; Lord Rathcavan and comedian Frank Carson.
Among the attendance were Lord Fitt's sister Rita;, the SDLP deputy leader Dr Alasdair McDonnell who was unable to attend the funeral at Westminster Cathedral in London due to the birth of a baby daughter on Tuesday; South Down SDLP Assembly member Margaret Ritchie and other party members. The Mass was held in the church where Gerry Fitt married his late wife Anne.