Former Stormont deputy first minister Seamus Mallon has died aged 83.

The ex-deputy leader of the nationalist SDLP and MP was an architect of the Northern Ireland peace process and a key figure in negotiating the 1998 Good Friday Agreement which largely halted violence.

He implemented the newborn political powersharing at the devolved parliament at Stormont and his former partner in government and ex-first minister Lord David Trimble said he was a committed democrat who lived up to his word.

Former prime minister Tony Blair negotiated the landmark peace deal with him and said he was a brave advocate of non-violence.

Current SDLP leader Colum Eastwood said: “In the darkest days of conflict, when hope was in short supply, Seamus represented the fierce thirst for justice that ran through the SDLP and through communities that had lost so much to political violence.”

Mr Mallon was a former teacher who lived in Markethill, Co Armagh, a largely Protestant town.

Just before the 1998 agreement was signed, he went to the houses of two lifelong friends from either side of the religious divide killed by loyalists in nearby Poyntzpass and vowed to seal the deal.

He joined Lord Trimble at the scene as a reminder of how important it was to prevent that from happening again.

Seamus Mallon
Seamus Mallon, right, with David Trimble, Bill Clinton and Tony Blair at Stormont (Paul Faith/PA)

Relations were later tested while in government by differences over the reform of policing but his unionist counterpart praised him for making and then implementing the agreement.

Lord Trimble said: “He had a lot to be proud of.

“That is a huge achievement.

“Even though from then to now there have been huge ups and downs in the political system, there has been no move away from peace.”

Mr Blair said he was one of the most important architects of non-violence.

“Brave, blunt, often prepared to swim against the tide if he felt it right, he was someone deeply respected and admired across the troubled landscape of Irish politics.

“Tough to negotiate with but always for a purpose. Even occasionally fierce but always wise.”

Former US President Bill Clinton, who was in office at the time of the Good Friday Agreement and championed peace talks in the 1990s, also paid a touching tribute to Mr Mallon.

He said: “From his earliest entry into politics, Seamus never wavered from his vision for a shared future where neighbours of all faiths could live in dignity—or from the belief he shared with John Hume and the entire SDLP that nonviolence was the only way to reach that goal.

“As his party’s chief negotiator in the talks leading to the Good Friday Agreement, he was respected by all parties for his intelligence and integrity, his candour and convictions.”

The SDLP spent the decades of violence advocating consensual constitutional politics in opposition to the IRA’s bloodshed.

Since 1998, it has been eclipsed in the political polls by Sinn Fein while Mr Trimble was ultimately replaced by his arch critic Ian Paisley at the head of the devolved administration.

Civil rights drew keen sportsman Mr Mallon into politics and the thoughtful and well-read political leader served as an MP for Newry and Armagh; an area which suffered greatly during the 30-year conflict.

Mr Eastwood said: “His passion for peace underpinned by truth, justice and reconciliation came from a lifetime as a proud son of Markethill, where he was born, grew up and raised his own family.

“It didn’t matter who you were, where you worshipped or what your politics were, there was always help to be found at Seamus’s hearth.”

Current Stormont first and deputy first ministers Arlene Foster and Michelle O’Neill also paid tribute.

Irish Taoiseach Leo Varadkar said he was a tireless champion of an inclusive Ireland.

The most senior Catholic cleric in Ireland, Archbishop of Armagh Eamon Martin, said Mr Mallon was a man of integrity and great courage.

“To his dying day, Seamus Mallon remained a man of hope for a brighter future – a shared and respectful future where we all experience a sense of belonging.”

Former Irish premier Bertie Ahern also paid tribute along with the current leader of Fianna Fail, Micheal Martin.