Ivan Cooper, one of the founders of Northern Ireland's civil rights movement, has died at the age of 75 after a long period of ill health.
The former Stormont MP, who helped found the SDLP, led the fateful civil rights march in Derry on Bloody Sunday when soldiers shot dead 14 protesters in January 1972.
He was also at the forefront of another landmark civil rights march in Derry in October 1968.
Many point to the scenes of violence when police moved to break up the demonstration on the city's Duke Street as the effective beginning of the Northern Ireland Troubles.
Mr Cooper was one of few Protestants involved with the civil rights movement.
He said his involvement saw him ostracised by other Protestants, and even found people in his church refused to sit beside him on the pews.
Mr Cooper is survived by wife Frances and daughters Sinead and Bronagh.
President Michael D Higgins presented Mr Cooper with a special award to mark his role in civil rights at an event to commemorate the 50th anniversary of the Duke Street march last year.
Today, Mr Higgins paid tribute: "As one of the organisers behind the earliest and many of the initiatives of the civil rights movement in Northern Ireland which were responding to the exclusion of so many from the most basic rights as housing, health and education, Ivan Cooper took inspiration from civic actions in the United States and became himself one of sources of inspiration for all those who took a stand against inequality and injustice.
"With his unshakeable belief in the universality and indivisibility of human rights, Ivan Cooper was a beacon of hope and the embodiment of the power of non-violent actions in pursuit of justice.
"His work as a campaigner in the 1960s was rewarded when he won the largest political mandate of any nationalist member of the Parliament of Northern Ireland and his legacy of personal courage, leadership and the dedication to the cause of justice continues to inspire activists and politicians alike."
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Current SDLP leader Colum Eastwood paid tribute, hailing Mr Cooper as a man who "embodied the contrasting traditions of this island".
"Ivan Cooper was born to break the mould," he said.
"A working class Protestant man who saw a common injustice and inequality that had taken root in Protestant and Catholic communities, he dedicated his life to fighting it.
"As an early leader in the civil rights movement, few have contributed as much to peace and equality on this island than Ivan.
"Organising marches in Derry for the right to a home, the right to a job and the right to a vote, Ivan often put himself in the path of danger to secure justice for people in every community.
"And on many occasions that meant that he suffered vilification and violence for his convictions. It never stopped him."
Ivan Cooper RIP. Physical frailty could not diminish his passion for justice, rights & peace. Even chat in weaker voice radiated strong conviction as he recalled or read events with both poignancy & wit - proving the natural oratory of his special voice for people & principles. pic.twitter.com/ojZa6hXTjR— Mark Durkan (@markdurkan) June 26, 2019
Mr Eastwood added: "Alongside his close friend John Hume, he helped blaze the trail on the path that led to the Good Friday Agreement.
"Anyone who knew Ivan knows that his selfless passion for justice continued to burn brightly into his later years. His unwavering belief that people on this island should come together to fight for common ideals and in their common interest is a lesson for us all. Especially as we face political division today.
"A man of sharp contrasts, sharp intellect and, it must be said, sharp tongue, he stands as a giant in the story of this island. And he holds a special place in the hearts of SDLP members."
Pat Hume, the wife of former SDLP leader John, who is himself suffering ill health, paid tribute to Mr Cooper.
"Ivan and John walked side by side, hand in hand, in their shared desire for equality, justice and peace in Ireland," she said.
"Ivan was the embodiment of the non-violent and non-sectarian movement for change that was the campaign for civil rights.
"His commitment and courage and his desire and determination to tackle these issues never waned. Nor did his friendship and relationship with John and me. He was loyal friend and constant visitor to John in recent years even as both battled ill-health.
"Ivan Cooper will forever hold a special place, not only in our hearts but in the history of this island and in the continuing of the fight for civil rights and social justice."
Actor James Nesbitt, who played Mr Cooper in the film Bloody Sunday, said: "He will be remembered as a politician of startling courage and conviction who passionately believed in equality for all.
"On a personal note his impact on my career was inestimable. Playing him in Bloody Sunday was a privilege and also a huge responsibility. Professionally it changed my life."