Coming in from the cold
But it marked the first crossing-of-the-paths encounter for the two personalities who now dominate Northern politics.
In 1964, Sinn Féin was a party that was not too far away from extinction. Its strength and numbers had been shredded by suppressive clampdowns on both sides of the Border during the late 1950s.
Beginning to regroup, it decided it would display the tricolour at its offices in West Belfast during the Westminster elections in contravention of the Flags and Emblems Act.
An emerging political figure on the unionist side, the Rev Ian Paisley, got wind of the gesture of defiance, and led street protests against the display of a "foreign" flag.
Back then there was none better when it came to unleashing hurricanes of hate with his tongue. Paisley's opportunistic and high-octane protests led to riots and the most serious street confrontations between Catholics and Protestants in Belfast for some years.
Gerry Adams was 16 years of age at the time. In his book 'Free Ireland: Towards a Lasting Peace', he recalls the incident as a forming influence.
"The tricolour played a role too in bringing me into politics Ian Paisley objected loudly to the display of the flag and threatened to march on Divis Street and remove it.
"The next day a force of RUC men broke down the door of the office and removed the flag. Two days of intense rioting followed . . . The government had responded to pressure from Paisley and had provoked a violent reaction from the Catholic working class."
That last sentence captures a lot of what became to be associated with both men in the succeeding four decades.
Paisley became the North's great agent provocateur, ratcheting up the conflict with his bile, his extremism and his intolerance, while never directly aligning himself or his party with violent elements. Adams, on the other hand, became and is the personification of the "violent reaction from the Catholic working class".
In two days' time, we may encounter the single biggest epoch-making event in over three decades of conflict, an agreement that will bring a permanent peace.
But though a historic breakthrough will usher in a power-sharing government between the DUP and the Sinn Féin, it's unlikely that we will see an iconic handshake akin to that of Yitshak Rabin and Yasser Arafat in the Middle East.
To contextualise that, you have to look at Paisley's long-standing refusal to treat with the Irish Government, a "foreign government" in his lexicon. Until he met Bertie Ahern in Government buildings this autumn, the only direct 'contact' Paisley had had with Irish Government figures was when he threw snowballs at them.
And Paisley has described Martin McGuinness, who will become the Deputy First Minister, in a new executive, as a man "whose hands drip with blood". The likelihood of warm handshakes in Hillsborough or Stormont is a remote one.
Nor will the agreement be interpreted by either side to use their own terminology as a "surrender". Paisley's evocation of a Biblical term "sackcloth and ashes" when demanding repentance of the IRA appealed to the anti-ecumenical, virulently pro-union sentiments of his base.
For republicans, the journey that Adams has led them on from violence to power-sharing and equality will also be portrayed as a victory, another milestone on the road to Irish unity.
Adams' violent past has been exhaustively documented. But one of the most intriguing questions is the extent to which Paisley contributed to the foment of violence in the North, and to prolonging the conflict? His rise from obscurity was remarkable, given that he was never aligned to any movement not founded by himself.
The son of a preacher, he was ordained at 20 years of age and co-founded the Free Presbyterian Church in Ravenhill, Belfast, when he was only 25.
By that stage he had already made his name as a fiery and firebrand preacher, with his rabble-rousing anti-Catholic oratory aimed very much at the Protestant working classes.
He also showed himself a master when it came to self-serving publicity gimmicks.
An early example of that was in 1958 when he persuaded a defrocked Spanish priest to perform mock Mass ceremonies as part of an anti-Catholic road show.
When Catholics had the temerity to complain, he responded with his trademark 17th century rhetoric: "We know your church to be the mother of harlots and the abomination of the earth."
His first foray into the political sphere was in 1959 when he formed the Ulster Protestant Association aimed at preventing Protestant dockworkers in Belfast joining Gerry Fitt's Irish Labour Party.
When the civil rights movement began to gather momentum in the late 1960s, it was Paisley's supporters who opposed them, often with the threat of violence.
In his recent autobiography, one of the civil rights leaders, Austin Currie, made a damning assessment of Paisley, whom he accused of having a malign influence.
"I have observed Ian Paisley for more than 40 years and I am of the belief that he has contributed more to the intensity and duration of the Troubles, and therefore to the deaths of so many people, than any other individual."
Worse than Adams, of whom Currie could not be counted as an admirer.
But this weekend as the final negotiations hovered between success and failure over 'visual' decommissioning the publication of photographs showing arms being destroyed Adams made his own pointed comments about Paisley's various flirtations with paramilitarism and violence.
There is a fair body of evidence to support that assertion. Some of his more blood-curdling sermons almost certainly incited Protestant mobs and paramilitaries to launch attacks against Catholics in Belfast and elsewhere.
In one notorious speech in the 1960s, he named specific addresses around the Shankill where Catholic families lived an exercise that resulted in Catholics being burned from their homes.
In the 1960s, a paramilitary group, the Ulster Protestant Volunteers, sprung up around Shankill Road. Initially, it was seen as an offshoot of Paisley's protestant group but Paisley dissociated himself once it began to acquire arms.
That pattern was to repeat itself in later years. Paisley, invoking his great hero Edward Carson, would threaten to form a mass Protestant army.
In an infamous incident in 1981, Paisley marched 500 men up a hillside late at night, each 'armed' with a firearms' licence. But, inevitably, he would distance himself from the groups once they started to acquire real firearms. However, there was a certain ambivalence there.
When it came to where Paisley stood when it came to loyalist violence, the waters were always muddied.
There was no such doubts about his Sinn Féin counterpart. Though Adams has always denied it, anybody who has read Ed Moloney's authoritative 'A Secret History of the IRA' will be left in little doubt that he was the pivotal figure of both the political and military side of republicanism from the mid-1970s on.
When the IRA agreed to enter ceasefire discussions with the British government in 1972, the organisation insisted that both Adams (then 23) and an even younger McGuinness be released from internment to be included in the IRA delegation to London.
Adams's natural sense of authority and his strategic clarity were already evident then, as was his arrogance.
The H-Block hunger strikes are said to have been a powerful forming experience for Adams's political development. Initially opposed to them, his hand was forced by the prisoners who would not be dissuaded.
According to Ed Moloney: "The deaths of 10 hunger strikers and the political turmoil that accompanied them had changed everything.
Bobby Sands' victory in the by-election of April 1981 and the success of H-Block candidates in the Republic's general election cleared the way for Adams and his supporters to openly argue for electoral politics.
"The scale of their flip-flop was huge . . . They pushed for a permanent strategy of fighting elections, a strategy that would co-exist, albeit uncomfortably with the IRA's armed struggle."
And thus was born the so-called Armalite and ballot box strategy, that would over the course of the next 20 years take the republican movement on a slow but inexorable journey away from violence.
In contrast, the 'not an inch' strategy was a constant for Paisley since the Democratic Unionist party was formed in 1971.
His grip on the party always seemed more iron-clad than that of Adams on Sinn Féin. The DUP opposed every single initiative for power-sharing, from the Sunningdale Agreement in 1974, to the Anglo-Irish Agreement in the mid-1980s, to the Good Friday Agreement (GFA) in 1998.
Paisley's natural constituency in the North was a working-class Protestant one, which had an antipathy for the establishment credentials of the UUP.
That of course led to the anomaly that at least some of those who voted for the DUP also tacitly supported loyalist paramilitary groups. While Paisley's own personal popularity among unionists was enormous, his party could never make sufficient inroads against the UUP.
Paisley's ambition to make his party the largest unionist party in the North seemed permanently thwarted with the UUP's electoral success in the wake of the GFA. However, in a sign of a shift in strategy by the DUP, his two most able deputies, Peter Robinson and Nigel Dodds, both accepted ministerial positions in the executive.
Paisley's hectoring, pedagogical public image was tempered by his personal warmth and wittiness, not often exposed to public view. There was a Jekyll and Hyde aspect to his make-up. As an MEP he made a notorious public protest when the Pope visited the European Parliament in Brussels.
Yet, he worked closely with fellow MEPs John Hume and Jim Nicholson on cross-party initiatives that benefited the North and paid a warm personal tribute to 'John' when he retired from politics.
Senator Maurice Hayes has made one of the most astute observations on this complex figure by saying that he has six personalities. "Two of them are very nice people, two quite awful, and the other two could go either way," he said.
Twenty-two years older than Adams, Paisley is clearly no longer the roaring table-thumping fundamentalist of old.
Last year, he looked frail and vulnerable during the Northern Assembly elections. His shoulders had shrunk and his once massive chest seemed to have caved in. In one nasty encounter with the UUP on the streets in Belfast, he had to be protected by Robinson and others when taunted by David Trimble.
"Why are you hiding Ian? I see the monkeys but where's the organ grinder?" shouted Trimble.
"I'd rather be a monkey than a buffoon like you," Robinson shouted back. But the image of a frail and defeated Paisley unable to defend himself sent out powerful optics.
Despite a mystery illness earlier this summer, Paisley's health seems rejuvenated now, just as his party's stock has risen. Ironically the man who moved might and main to block all compromise, is now on the cusp of delivering the last great compromise in Northern politics.
But true to form, the two players may forge a deal without having met face-to-face, relying on intermediaries from the Irish and British governments.
"Things fall apart, the centre never holds," Yeats wrote when reflecting on the anarchy that was unleashed in Ireland at the beginning of the 20th century.
Moderate voices have ultimately lost out too in the North. There may be no handshakes on Wednesday. But it will see a remarkable culmination after 40 years two politicians who started at the fringes and more or less represented the extreme positions of both sides right at the centre of things.


