Mr Seamus Mallon, the SDLP deputy leader who was the party's chief negotiator in the all-party talks, has been the MP for Newry and Armagh since 1986. He has a reputation for being trenchant and outspoken and has been described as a hard-edged nationalist. Vehemently anti-violence, Mr Mallon is also renowned for his stubbornness and honesty.
Ulster Unionist MP Mr Ken Maginnis once said of him: "We disagree fundamentally on many issues but he's truthful and principled and straight as a die. I`ve never know Seamus Mallon to tell a lie."
A man of formidable intellect, Mr Mallon's interests range from literature to golf, poker, good whiskey, Gaelic football and horse-racing. He also has a successful background in amateur dramatics. His one-act play, Adam's Children, won an all-Ireland drama festival in 1969.
Born into a middle-class family in the mainly Protestant village of Markethill, Co Armagh, his father was headmaster of a local primary school. This was a post which Mr Mallon himself later held.
His introduction into public life was in 1962 when a local unionist councillor refused to rehouse a large Catholic family. He decided to do something about it and threw himself into the civil rights movement.
He joined the SDLP and became a councillor in 1973 and resigned as a school principal. He just missed a place in the powersharing executive. He was elected chairman of the SDLP assembly members.
After the fall in 1976 of the Northern Ireland Convention, of which he was a member, he had no substantial income. He returned to part-time teaching to provide for his family.
In 1979, he became the SDLP's deputy leader and the party's justice spokesman. The early 1980s were difficult for him. Mr Mallon demanded that the RUC prove that it was not operating a shoot-to-kill policy. After speaking out against the security forces, there were death threats, anonymous phone calls and verbal abuse. His home was petrol bombed.
In 1982, he was appointed a member of the Seanad by the then Taoiseach, Mr Charles Haughey, a move which led to Mr Mallon being disqualified from the Northern Assembly of which he was also a member. This lasted only a short time as the Fianna Fail government was defeated.
He stood for Westminster unsuccessfully three times. He finally became an MP in 1986 after the Ulster Unionist MP, Mr Jim Nicholson, resigned in protest at the Anglo-Irish Agreement. When he entered the House of Commons, he took the affirmation rather than the oath of allegiance.
It is common knowledge that for years a tension has existed between him and Mr John Hume but there is a common purpose which binds and they respect each other. Within the SDLP, it was always Mr Mallon's task to rally the grassroots and he makes the most interesting speeches at SDLP conferences.
Mr Mallon is now 61 and has angina and low blood pressure. He has to rest if they are active. He took ill while at Westminster in 1996, when he had a prolonged coughing fit while on radio.
In his younger days, he was an active sportsman, playing soccer on a Saturday afternoon, rugby in the evening and Gaelic football on Sunday. Nowadays, he plays golf.
Mr Mallon is said by colleagues to be a private man. He is a practising Catholic and an opponent of abortion. He lives with his wife in a bungalow overlooking Markethill.