The pinnacle of Seamus Mallon's political career was his rise to the role of deputy first minister in the new Northern Ireland Assembly.
It came weeks after the Good Friday Agreement was forged in 1998.
If SDLP leader John Hume was the architect of that agreement then his deputy, Seamus Mallon, was the careful builder.
He was one of the oldest hands in Irish politics and played a central role in the peace process.
Sometimes abrasive, often humorous, with a sharp intellect, he earned the respect of many unionists as an honest spokesman for nationalism.
Famously, within a year of becoming deputy first minister, he resigned in protest at delays in establishing power sharing.
He felt the then first minster, David Trimble, was violating the agreement by insisting on weapons decommissioning.
When a deal over guns and government was brokered, Mallon was allowed to "de-resign" in November 1999.
He and his new partner, Trimble, were dubbed the political "odd couple". But the pair were united against violence.
On one memorable occasion, Mallon and Trimble went together to comfort two families after the murders of two friends, Philip Allen and Damien Trainor - one a Protestant and one a Roman Catholic - in Poyntzpass, County Armagh, in March 1998.
Both politicians said their presence there together was a sign of solidarity against the men of violence.
Mallon was vehemently against violence from whatever side it came and had tough words for gunmen of all shades.
He was born in Markethill in 1936, the son of a headmaster and a nurse. He, too, became a headmaster in a primary school.
He said he was drawn into the civil rights movement and into politics because of the discrimination he witnessed in his home town.
"The family of one of my pupils was trying to get out of a horribly dilapidated home and into a council house," he said.
"At that time, councillors had the power of allocation. That family was turned down by a [unionist] councillor who said: 'No Catholic pig and his litter will ever get a home in Markethill while I am here!'"
Seamus Mallon helped form the SDLP. By 1973, he was a councillor and became the SDLP's deputy leader within five years.
Throughout the Troubles, he was a stern critic of the security forces. Nor did he hesitate to speak out against the IRA. His frankness led to death threats and attacks on his family home.
He was to be a deputy for most of his political life. In the SDLP, he worked in the shadow of John Hume.
Publicly, they appeared formidable, but privately there were strains, not least over Hume's failure to tell Mallon about his secret peace talks with Sinn Féin leader Gerry Adams.
He was an assembly member in the Sunningdale power sharing assembly and later famously dubbed the Good Friday Agreement as "Sunningdale for slow learners".
In 1982, he was briefly an Irish senator and was unseated from the NI Assembly because he had been a member of the senate at the time of the election.
He was an Irish nationalist to the core, but he loved the theatre of debate at Westminster in his role as MP for Newry and Armagh.
He was said to possess one of the sharpest minds in Northern Ireland politics and, as deputy first minister, he got his chance to shine in the new assembly.
His vision of a new policing service brought him into conflict with the then Secretary of State Peter Mandelson whom he accused of betrayal and "political chicanery" over promises made.
After years spent highlighting alleged collusion between the Royal Ulster Constabulary (RUC) and loyalist paramilitaries, he fought hard at the Weston Park talks in 2001 to achieve police reform. Weeks later, he made a dramatic call to nationalists to give the new police service a chance.
When John Hume left the leadership of the SDLP, Seamus Mallon said he would not pursue the post - he felt he was too old for the job.
After the many trials and tribulations of holding the post of deputy first minister at Stormont between 1998 and 2001, he stepped down at the age of 65.
In 2013, Mallon and Trimble received honorary doctorates from Dublin City University to mark the 15th anniversary of the Agreement.
At that stage, Mallon criticised the Northern Ireland Executive, saying that they had failed to address "the most important issues".
In an interview for Irish broadcaster RTÉ at that time, he said that the middle ground in Northern Ireland had "paid the price" for the agreement.
In 2015, talking on BBC Radio Ulster's Talkback, he claimed that Sinn Féin had used John Hume to gain respectability in the United States.
Hume was "no fool", he said, but Sinn Féin leaders played him "like a 3lb trout". However, he also said that any sacrifice the SDLP made was worth it if it saved a single life.
Speaking on the 20th anniversary of the Good Friday Agreement in April 2018, Mallon said he felt both "sad" and "very angry" at the political stalemate at Stormont between the DUP and Sinn Féin.
"I watch the hypocrisies which are unbelievable and the untruths which are believable," he said.
"Politics has been debased and diminished by these two political silos which have almost balkanised the Northern Ireland that I live in."
Seamus Mallon was a committed nationalist aspiring to Irish unity, but in 2019 said a simple 50% plus one majority in a border referendum would not "give us the kind of agreed and peaceful Ireland we seek".
He believed there should be "parallel consent", involving a majority of both unionist and nationalist voters.
"If we are going to have any integrity in terms of Irish republicanism, then it has got to be an organic thing," he once said.
"It has to look into the unionist heart as well as the unionist mind. We've got to make unionism part of Irish life."