LONDON, England (AP) — David Trimble, a former Northern Ireland first minister who won the Nobel Peace Prize for playing a key role in helping end Northern Ireland’s decades of violence, has died, the Ulster Unionist Party (UUP) said Monday. He was 77.

The party said in a statement on behalf of the Trimble family that the unionist politician died earlier Monday “following a short illness”.

Trimble, who led the UUP from 1995 to 2005, was a key architect of the 1998 Good Friday Agreement that ended three decades of violent conflict in Northern Ireland known as “The Troubles”.

Keir Starmer, leader of Britain’s Opposition Labour Party, called Trimble “a towering figure of Northern Ireland and British politics” in a tweet Monday. Current UUP leader Doug Beattie praised Trimble as “man of courage and vision”, a tribute echoed by leaders from across the political divide.

The UUP was Northern Ireland’s largest Protestant unionist party when, led by Trimble, it agreed to the Good Friday peace accord.

Although a hardliner unionist when he was younger, Trimble became a politician whose efforts in compromise became pivotal in bringing together unionists and nationalists in Northern Ireland’s new power-sharing government.

Like most Protestant politicians at the time, Trimble initially opposed efforts to share power with Catholics as something that would jeopardise Northern Ireland’s union with Britain. He at first refused to speak directly with Gerry Adams, leader of Sinn Fein, the political wing of the Irish Republican Army.

He ultimately relented and in 1997 became the first unionist leader to negotiate with Sinn Fein.

Former British Prime Minister John Major said Trimble’s “brave and principled change of policy” was critical to peace in Northern Ireland.

“He thoroughly merits an honourable place amongst peacemakers,” Major said.

The peace talks began formally in 1998 and was overseen by neutral figures like former US Secretary George Mitchell. The outcomes were overwhelmingly ratified by public referendums in both parts of Ireland.

Trimble shared the 1998 Nobel Peace Prize with Catholic moderate leader John Hume, head of the Social Democratic and Labour Party, for their work.

Trimble was elected first minister in Northern Ireland’s first power-sharing government the same year, with the SDLP’s Seamus Mallon as deputy first minister.

But both the UUP and the SDLP soon saw themselves eclipsed by more hardline parties — the Democratic Unionist Party and Sinn Fein. Many in Northern Ireland grew tired of Trimble and his colleagues, who appeared to be too moderate and compromising.

Trimble struggled to keep his party together as the power-sharing government was rocked by disagreements over disarming the IRA and other paramilitary groups. Senior colleagues defected to the DUP, Trimble lost his seat in Britain’s Parliament in 2005 and soon after he resigned as party leader. The following year he was appointed to the upper chamber of Parliament, the House of Lords.

Northern Ireland power-sharing has gone through many crises since then — but the peace settlement has largely endured.

“The Good Friday Agreement is something which everybody in Northern Ireland has been able to agree with,” Trimble said earlier this year. “It doesn’t mean they agree with everything. There are aspects which some people thought were a mistake, but the basic thing is that this was agreed.”

William David Trimble was born in Belfast on October 15, 1944, and was educated at Queen’s University, Belfast.

He had an academic career in law before entering politics in the early 1970s, when he became involved in the hardline Vanguard Party. He surprised many when he won the leadership of the UUP in 1995.

Trimble was not always a popular leader, and his negotiations toward the peace accord attracted criticism from elements of his party.

“David faced huge challenges when he led the Ulster Unionist Party in the Good Friday Agreement negotiations and persuaded his party to sign on for it,” Adams said Monday in a statement. “It is to his credit that he supported that Agreement. I thank him for that.”

“While we held fundamentally different political opinions on the way forward nonetheless I believe he was committed to making the peace process work,” Adams continued. “David’s contribution to the Good Friday Agreement and to the quarter-century of relative peace that followed cannot be underestimated.”

Trimble is survived by his wife Daphne and children Richard, Victoria, Nicholas and Sarah.