Adams - shrewd but ruthless leader
Gerry Adams represents the most recognisable public face of Sinn Fein.
He defended IRA gunmen for a substantial period of the conflict which disfigured and devastated Northern Ireland for 25 years.
But in 2007 he dramatically agreed to join an historic power-sharing Government in Stormont with his old arch-enemy the Rev Ian Paisley.
It was the sensational climax to years of bitterness, hatred, bloodshed and violence - a rapprochement than 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 Great Britain.
He was the prime figure in the negotiations before the 1994 IRA ceasefire following the historic Downing Street declaration a year earlier.
But 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 Prime Minister Tony Blair.
Because of his reputed influence and power over IRA gunmen, 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 earlier, the broadcast ban on him was lifted in 1994, Adams became a hot property on TV to the despair of those who, in the words of 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 former Prime Minister John Major and the then Irish Premier, Albert Reynolds - Mr Adams showed no signs of weakening or wavering in his unshakable resolve to achieve a united Ireland.
His greatest ally, outside his own nationalist comrades, was 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 Day celebrations.
The President had already granted him a visa to visit the US - his second - but this time had permitted him to use his stay as a fund-raising event.
It succeeded in creating an icy rift between President Clinton and a furious Mr Major but ultimately was part of a process culminating in peace.
It had been a lengthy journey for Sinn Fein.
Its recognition as a political party in its own right saw Mr Adams made vice-president and arguing that links with the Irish Dail should be set up and the IRA should recognise British courts instead of claiming their offences were political.
Mr Adams was a past-master at rationalising the atrocities committed by the IRA.
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."
But he was always, nevertheless, 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, where 10 men starved themselves to death, he advocated the policy of the "ballot box and the Armalite" with the emphasis on a broader political base.
He stood for Parliament in 1983 and won but refused to take up his seat because he would have had to swear allegience 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 the UK. 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 Grand Hotel, Brighton bombing at the Tory Party conference - which so nearly killed Margaret Thatcher - was hailed by him as "a blow for democracy".
The following year Mr Adams became president of Sinn Fein.
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 Dail as well as in Northern Ireland, where Sinn Fein 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.
Once, shortly before the 1994 ceasefire, he was photographed acting as a pall-bearer at the funeral of an IRA man, killed during an act of terrorism.
This was the coffin of Shankil bomber Thomas Begley, on its way to the republican plot at Milltown Cemetery.
Away from politics he lived with his wife Colette and their son Geroid in a fortified house in the intensely republican Andersonstown area of Belfast. He also moved, for security reasons, from time to time to a succession of safe houses throughout the city.
Mr Adams 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 as a member of Ireland's Dail for the border constituency of Louth.
Since devolution Sinn Fein, headed by Martin McGuinness in the Assembly, has voted to accept policing and justice powers in Northern Ireland but power-sharing with their partners in the Democratic Unionists has become increasingly fractious.
Mr Adams' focus from Louth has been on expanding Sinn Fein's presence south of the border and fighting a campaign for European seats in both jurisdictions.
His arrest will undoubtedly provide a talking point as the electoral campaign warms up.