HE represents the most recognisable public face of Sinn Féin.
Gerry Adams defended IRA gunmen for a substantial period of the conflict which disfigured and devastated the North for 25 years.
But in 2007 he dramatically agreed to join a historic power-sharing government in Stormont with his arch-enemy, Ian Paisley.
It was the sensational climax to years of bitterness, hatred, and violence — a rapprochement that nobody believed would ever happen.
Mr Adams once pulled pints of Guinness in a Belfast bar and then became a hate figure amongst unionists and throughout Britain.
He was the prime figure in the negotiations before the 1994 IRA ceasefire following the historic Downing Street declaration a year earlier.
However, Mr Adams, always impeccably dressed and immaculately groomed, is known as a shrewd political bargainer, and a man who was able to rouse a sympathetic audience to raptures with his republican appeal.
And in the run-up to the Good Friday Agreement of 1998, which enabled power-sharing, the release of paramilitary prisoners, and ultimately the destruction of IRA arms, Mr Adams made history by visiting 10 Downing Street at the invitation of the British prime minister, Tony Blair.
Because of his reputed influence and power over IRA gunmen, Mr Adams was regarded by Downing Street as a key element in the process, someone to keep “on side”.
However, Mr Adams, 65, has always regularly denied involvement in the IRA.
And when the broadcast ban on him was lifted in 1994, Mr Adams became a hot property on TV, to the despair of those who, in the words of former British prime minister Margaret Thatcher, believed the IRA should be deprived the “oxygen of publicity”.
Despite the ceasefire and the long disputes over the Downing Street Declaration — forged by British prime minister of the time John Major and then taoiseach, Albert Reynolds — Mr Adams showed no signs of weakening or wavering in his unshakeable resolve to achieve a united Ireland.
His greatest ally, outside his own nationalist comrades, was US president Bill Clinton who, recognising the value of Irish votes in the US, enraged Mr Major in 1995 by inviting Mr Adams to the White House for the St Patrick’s Day celebrations.
Clinton had already granted him a visa to visit the US — his second — but this time had permitted him to use his stay as a fundraising event. It succeeded in creating an icy rift between Mr Clinton and a furious Mr Major, but ultimately was part of a process culminating in peace.
It had been a lengthy journey for Sinn Féin. Its recognition as a political party in its own right saw Mr Adams made vice-president and arguing that links with the Dáil should be set up and the IRA should recognise British courts instead of claiming their offences were political.
Portentously, however, he seemed to recognise the futility of military means in 1980, saying: “The British realise there can be no military victory. It is time that republicans realised there can be no military victory.”
nevertheless, he has always been reluctant to condemn violence. On a rare visit to Brighton to address a fringe meeting at the 1983 Labour Party conference, he said: “I will not be prepared to condemn the legitimate use of armed struggle by the republicans against the British.”
After the 1981 H-Block hunger strikes, he advocated the policy of the “ballot box and the Armalite” with the emphasis on a broader political base. He stood for British parliament in 1983 and won, but refused to take up his seat because he would have had to swear allegiance to the queen. He fought and won West Belfast seats at subsequent Westminster elections, but always refused to take his seat.
He did work for his constituents, however, using the power of his office to improve conditions for many in one of the most deprived areas of Ireland or Britain. People living in the Falls Road or Andersonstown had nothing but praise for him. “He got things done,” they said.
Loyalists shot him in 1983, wounding him in the neck, shoulders, and arm. Three other men in the same car were also wounded.
The 1984 bombing at the Tory Party conference at the Grand Hotel, Brighton — which nearly killed Ms Thatcher — was hailed by him as “a blow for democracy”.
The following year, Mr Adams became president of Sinn Féin.
After the Enniskillen Remembrance Day massacre of worshippers at a Poppy Day service, he expressed regret at the deaths and attempted to dissociate himself from the tragedy.
He had set his sights on taking seats in the Dáil as well as in the North, where Sinn Féin councillors had become commonplace.
Yet this enigmatic but ruthless political operator could be found by the gravesides of IRA “martyrs”, watching as the balaclava-clad gunmen fired shots over coffins.
Away from politics, he lived with his wife Colette and their son Gearóid in a fortified house in the intensely republican Andersonstown area of Belfast. For security reasons, he also moved, from time to time, to a succession of safe houses.
He was part of the Northern Ireland Assembly during its early years following the Good Friday Agreement but in 2010 he resigned his Westminster seat and stood for election to the Dáil in Louth.
Since devolution, Sinn Féin, headed in the Northern Assembly by Martin McGuinness, has voted to accept policing and justice powers in the North, but power-sharing with their partners in the Democratic Unionists has become increasingly fractious.
Mr Adams’s focus from Louth has been on expanding Sinn Féin’s presence in the south and fighting a campaign for European seats in both jurisdictions. His arrest will undoubtedly provide a talking point as the electoral campaign warms up.