Eddie McGrady, one of Northern Ireland's longest serving politicians, has died aged 78.
He was a founding member of the nationalist Social Democratic and Labour Party.
The SDLP stalwart made the South Down constituency his own after ousting Enoch Powell as MP in 1987 - and represented the area at Westminster until 2010, when he made way for Margaret Ritchie.
The party said he died on Monday after a long illness.
John Hume, former party leader and fellow founding member, paid tribute to his "dear friend".
"Eddie was a man of deep faith, incredible fortitude and considerable courage. He brought a sharp political instinct to all his work, displaying both talent and tenacity throughout a distinguished career stretching 50 years in public service," he said.
"He will be rightfully remembered for his 1987 election victory over Enoch Powell but we should not forget his unswerving devotion to peace and his substantial contribution towards the new beginning to policing."
Mr Hume added: "Eddie served the constituency of South Down which he loved with distinction but above all Eddie was a family man happiest at his home in Saul in Downpatrick.
"I wish to send my deepest condolences to his daughter Paula, sons Jerome and Conaill his sister Maire, brother Malachy and wider family circle."
Leader Alasdair McDonnell MP described Mr McGrady as "one of the founding pillars of the party" and said the country had lost "a person of faith and integrity".
"I am deeply saddened to learn of the death of Eddie McGrady - a great patriot and a great democrat whose contribution to this community at many levels has been incalculable," said Dr McDonnell.
"County Down has lost a great champion and Ireland has lost a person of faith and integrity who enhanced public life in a political career that lasted almost half a century.
"As a founding member of the SDLP, Eddie helped to shape not only our party, but history, as he along with John Hume, Seamus Mallon and others helped to define the politics of an era and build the peace of our lifetime."
Margaret Ritchie MP, who was mentored by Eddie McGrady, said he was an inspiration to a generation of politicians and "a true advocate for the community of South Down".
"During his political career from the time he entered political life as a councillor on Downpatrick Urban Council to his years as MP for South Down, Eddie built up a great infrastructure for the people of South Down and always put South Down first," she said.
"Eddie was a great campaigner and he gave his and future generations the confidence that politics and campaigning can bring about change locally and regionally through his role in the peace process.
"Eddie will be sadly missed."
Mr McGrady had attended the recent office opening of Seán Rogers MLA in Newcastle where, despite ill health, he was determined to show his support.
SDLP members had paid tribute to Mr McGrady at the weekend's 42nd annual party conference in Armagh - only the second conference he had missed.
Dr McDonnell had said the message from his hospital bed was to "just get out there and finish the job".
Mr McGrady, from Downpatrick, was a former chartered accountant. He sat on Downpatrick Urban council in the 1960s and early 1970s, and then on the Down District Council until 1989.
In 1970 he became a founder member of the SDLP later serving as its first chairman, from 1971-1973.
The veteran politician had romped home with a majority of almost 14,000 votes in the 2001 general election.
And when he announced he would stand down in 2010 he said it had been “a great honour and privilege” to serve at various stages as a councillor, Assembly member and MP.
"I have spent 23 years as an MP representing all the people of South Down and democratic Irish nationalism in the House of Commons," he said.
“I know if SDLP leaders had not been there to challenge the British Government, to act in the interests of the Irish people, nationalists and unionists, and to demand justice and equality for all, we would not have peace and no prospect of a better future.”
Mr McGrady was married to Patricia for more than 40 years. Sadly, she passed away after illness in 2003.
He is survived by their three children Paula, Jerry and Conaill.