One of the key architects of the loyalist ceasefires has lauded Albert Reynolds' enormous contribution to the peace process.
Billy Hutchinson was once an Ulster Volunteer Force (UVF) gunman and prisoner who helped spearhead moves to end Northern Ireland violence in 1994.
He said the former taoiseach was well thought of by loyalist ceasefire negotiators.
"Albert Reynolds was highly regarded by David Ervine and Gusty Spence through his engagement with them to reassure loyalists around the intentions of the Irish Government following the ceasefires.
"He will be remembered for this contribution and his wider role with republicans."
Unionists from across the spectrum have paid tribute to the statesman and said he had a cautious and careful approach to negotiations which led to IRA and loyalist ceasefires and the Good Friday peace agreement four years later.
Mr Hutchinson said: "Albert Reynolds made an enormous contribution to the peace process and I am very saddened to hear of his death."
Lord Robin Eames, the retired head of the Church of Ireland who was heavily involved with the governments during the years surrounding the end of the conflict, said the former taoiseach recognised the importance of obtaining consent by all to any future constitutional change.
"He made strenuous efforts to understand and articulate the feelings of Protestant and unionist people at a time of immense pressure, suffering and uncertainty for this community.
"He showed great courage in making contact with the Northern community and history must recognise the significant role he and John Major played in bringing about the ultimate cessation of the Troubles."
The Downing Street Declaration was made by Mr Reynolds in December 1993 alongside the then British prime minister Sir John Major.
It espoused principles combining consent to constitutional change and power-sharing with an Irish dimension.
Retired Presbyterian minister the Reverend Ken Newell helped pioneer cross-community relations with Catholics to encourage peace.
"I know that he was a door-opener for Sinn Fein, he opened the door and brought them in from the cold."
Jeffrey Donaldson, a former Ulster Unionist and now Democratic Unionist MP, said unionists could not have taken their own steps towards peace without his acceptance of the need for change.
"Albert Reynolds was the first Irish prime minister who understood and supported the principle of consent in relation to Northern Ireland. He had an understanding of Northern Ireland and the Republic's relationship with the whole of the UK which was beyond many of his counterparts.
"There can be no doubt that he was committed to seeking peace, and whilst unionists will have been critical of some aspects, there can be no doubt about his legacy in terms of Northern Ireland."
However, another senior unionist negotiator has claimed he missed an earlier opportunity to do a deal on ending violence.
Sir Reg Empey alleged more lives could have been saved if agreement had been reached in 1991 or 1992 rather than in 1998.
The stumbling block emerged as unionists wanted the Irish government to commit to dropping articles two and three of the Republic's constitution, which asserted sovereignty over Northern Ireland. According to the Ulster Unionist, Mr Reynolds refused and an opportunity was lost.
The constitutional change was eventually made as part of the agreement that cemented an on/off IRA ceasefire and led to devolution of political powers from London to Belfast and ultimately to paramilitary weapons decommissioning.
Sir Reg said: "We could have had an agreement in about 1991 and it foundered on the difference between could and would, so Reynolds must have endorsed that and it was a missed opportunity.
"I think there was a deal on the table and it could have happened if we had been able to do that; when you think about it in 1991 we could have had a deal seven years before we got one and a lot of people might not have lost their lives had it been possible."
The former UUP leader added that the then recently appointed incumbent was not strong enough to do a deal.
Another Ulster Unionist peer, Lord Ken Maginnis, concurred.
He said: "He was a cautious protector of Fianna Fail's position rather than a critical negotiator.
"I think he found himself in a position that quite honestly he would not particularly have wanted to be in."
He added: "He never was going to be a shaker and mover. He just knew that he was not going to get Fianna Fail anywhere and hence to some extent that was the end of his responsibility.
"He was keener not to fall out with people than he was somehow to do some long-term deal."