The boy from Bogside who was Britain's 'number one terrorist' - but also a chief negotiator in lasting peace
Once described as "Britain's number one terrorist", Sinn Féin's Martin McGuinness played a major role in the Northern Ireland peace process.
Widely accepted as a one-time IRA chief of staff, Mr McGuinness (66) moved from his army role to successfully share political power with one of his deadliest enemies.
Not alone did he share power with anti-republican DUP leader Ian Paisley, the two got on so well together they were dubbed the "Chuckle Brothers".
Born in 1950, Mr McGuinness is the second eldest of seven children. His father William worked in an iron foundry and the family of nine lived in a two-bedroomed house in the Bogside in Derry. His mother Peggy was originally from Donegal.
When he left school at 15 he experienced sectarianism first hand. He was rejected for a job as a mechanic because of his Catholic religion.
His determination to fight the Republican battle solidified when Seamus Cusack (28) and Desmond Beattie (19) were shot dead in Derry on the same day by British soldiers in July 1971.
Although a former teacher had described Mr McGuinness as a well-mannered student who was "not outstanding in any way", he found his calling as a focused IRA activist.
His reputation grew. During the 16 months up to December 1972 a total of 26 British soldiers were killed by the Provisional IRA in Derry.
Years later Mr McGuinness said: "I was proud to be a member of the IRA. I am still - 40 years on - proud that I was a member of the IRA.
"I believed that in a situation where the community that I came from were being treated like second- and third-class citizens that I had a responsibility to fight back against it. And I don't apologise to anybody for having done that. I think it was the right thing to do."
Asked at another point if he felt guilty about people who had died, he responded: "I do have a very deep sense of regret that there was a conflict, and that people lost their lives, and you know, many were responsible for that - and a lot of them wear pinstripe suits in London today. So I think if people want to apportion responsibility and blame for all of that it's going to have to be apportioned and shared out all over the place."
In July 1972, Mr McGuinness was part of a seven-member IRA delegation flown to London to meet Northern Ireland Secretary of State William Whitelaw to try to end the Troubles. These talks were unsuccessful.
The following year the Special Criminal Court in Dublin sentenced Mr McGuinness to six months in prison for IRA membership. He had been caught in a car containing large quantities of explosives and ammunition.
He refused to recognise the court and declared his membership of the IRA.
His switch to politics came in 1983 when he contested elections for the British House of Commons. He was finally elected in 1997, after three failed attempts, to represent Mid Ulster.
Mr McGuinness refused to take the seat in line with Sinn Féin party policy as it would have involved swearing an oath of allegiance to the British Crown.
He was re-elected to the seat in 2001, 2005 and 2010.
In the 1990s, the 'Cook Report' on ITV claimed he was "Britain's number one terrorist", fuelling unionist calls for Sinn Féin to be banned. He and other Sinn Féin figures responded with a series of counter-attacks on the 'Cook Report'.
Meanwhile, during the 1990s he was the IRA's chief negotiator in secret talks that ultimately brought about the Good Friday Agreement in 1998. This pact ended the conflict, and Mr McGuinness was appointed education minister in the new Northern Ireland Assembly.
One of his first decisions was to eliminate the controversial 11-plus examination which he himself had failed 38 years previously.
The assembly was suspended after disagreements over issues like policing and the decommissioning of arms, but a new agreement was reached in 2006.
Sinn Féin and the Democratic Unionist Party became the two largest parties in the assembly and formed a coalition.
Mr McGuinness was appointed deputy first minister with DUP leader Mr Paisley as first minister.
The two bitter enemies became firm friends and after Mr Paisley's death in 2014 his wife Eileen revealed Mr McGuinness had been very supportive to her family.
When Mr Paisley retired in 2008, Mr McGuinness worked as deputy to then-first minister Peter Robinson, who was considered to be even more anti-republican than his predecessor. In 2010, the pair agreed on the transfer of powers from Britain to Northern Ireland and were both re-elected in 2011.
Later that year, Mr McGuinness stepped down from his assembly post to run in the presidential election in the South. When he finished third in that race, he returned to the assembly.
But his relationship with Arlene Foster, who took over as first minister in 2015, has been far more strained.
Mrs Foster spoke of her difficulties with Mr McGuinness because he delivered a graveside oration for the IRA man she believed tried to murder her father.
She said, however, she would still work with Mr McGuinness as "the past is the past".
He was opposed to Brexit and concerned it would see the return of a "hard Border" between the North and South of Ireland.
In recent months he has battled ill-health, although he yesterday insisted it has "absolutely nothing" to do with his resignation.
In early December, he withdrew from a planned visit to China on medical advice and Mrs Foster travelled without him.
In an interview before Christmas, Mr McGuinness said: "I am being attended to by a wonderful group of doctors and nurses from our health service and I think that's all I have to say about it at the moment."
He has never let go of his view that Ireland would be united. "I believe a united Ireland is inevitable. Absolutely, but I believe it can only happen by peaceful and democratic means," he said.