John Hume and Seamus Mallon - the two big beasts of the SDLP in its heyday - had an open row about whether nationalists really cared about a united Ireland.
The party leader and his deputy, whose differences were mostly kept under wraps during their dominance of northern nationalism for much of the Troubles, were fundamentally split on the definitive issue.
The schism erupted during a meal at the Irish Embassy in London in January 1986. They had been invited, along with other SDLP members and family, by then ambassador Noel Dorr to mark Mr Mallon officially taking his newly won Newry and Armagh seat for the first time at Westminster.
In a missive - marked 'secret' - sent back to Dublin, Mr Dorr told the Irish Government "considerable differences of outlook and approach between John Hume and Seamus Mallon came out quite clearly in discussion".
"An argument developed between them in which Hume spoke of the ambivalence of Northern nationalists about Irish unity - they want it but they know the time is not ripe for it and the concept of unity is more important as a factor in what he called 'the tribal conflict' than in itself," the diplomat reported.
Mr Hume argued that his native and predominantly nationalist Derry had closer links with Glasgow than the west of Ireland or even Dublin, according to the newly declassified documents released into the National Archives.
"Mallon on the other hand disagreed with this and spoke of the desire for Irish unity as a deep motivating force North and South of the border," Mr Dorr said in the letter, which was copied to the Taoiseach Garret FitzGerald and Tanaiste Dick Spring.
"He also challenged Hume's view that Irish unity, of necessity, would have to be a very long-term prospect.
"Mallon sees the Anglo-Irish Agreement as a kind of last throw by constitutional Irish nationalism."
The fledgling Agreement had been signed just two months beforehand and was facing a revolt from unionists.
Mr Mallon told the dinner party if it failed the outlook would be "bleak".
But his party leader "dissented" from this analysis - insisting the treaty that gave Dublin an advisory role in Northern Ireland was a new beginning rather than a last opportunity.
Mr Hume argued that a substantial number of Northern Catholics would never support violence in any circumstances, and agreed with a suggestion that there would be "another agreement if the Anglo-Irish Agreement failed".
The pair also appeared to differ on what direction the SDLP should take in the immediate aftermath of the Agreement.
Mr Hume said the choice was to "play it safe" by appealing to its own supporters, or to reach out to unionists to resolve the "fundamental historic problem".
He strongly favoured reaching out to unionists and wanted to do it sooner rather than later.
But Mr Mallon had a "longer timetable in mind" and said his voters - many of whom gave him conditional support - were giving the Agreement a chance and wanted to see it delivered.
In the letter, Mr Dorr appeals for discretion around his report as he was sure neither Mr Hume nor Mr Mallon would appreciate having their differences talked about.
Robin Eames' elevation to Archbishop of Armagh caused consternation among his Catholic counterparts - who thought he was a "cold fish".
In a meeting between Cardinal Tomas O Fiach and an Irish Government official in 1986, the Catholic Church leader let it be known he was less than enthusiastic about his new ecclesiastical neighbour.
"Eames, whom he has known for years, has a poor ecumenical record and, at the personal level, is something of a 'cold fish'," the official reported being told by Cardinal O Fiach in a missive to the Taoiseach's office. The Catholic leader indicated he would have preferred Bishop of Derry and Raphoe James Mehaffey to take up the position as his opposite number in Armagh. Lord Eames (below) was active in Ulster Unionist circles, said Cardinal O Fiach, but he remarked he would keep an "open mind" about him, as he appeared constructive about the recently-signed Anglo-Irish Agreement.
Separately, Bishop Cathal Daly - who went on to become Catholic Archbishop of Armagh - also confided in an Irish official in February 1986 that he had his doubts about the new Anglican leader.
"From his time as Bishop of Derry and Raphoe, Eames does not have a good record as an ecumenist and in private conversation his unionist views emerge quite clearly," Bishop Daly said, according to a note of the meeting.
Bishop Day hoped that Eames' responsibility for the Church of Ireland on both sides of the border "will cause him to offer more balanced views in future".
By Brian Hutton
Northern Ireland's top civil servant suggested "doing nothing" to tackle loyalist violence to teach unionists that it "does not pay".
Sir Kenneth Bloomfield, who went on to become the region's Victims Commissioner, told Irish officials during a confidential meeting in April 1986 that a "completely logical line of action" amid increasing unrest would be no action at all.
There was a ferocious unionist backlash at the time to the Anglo-Irish Agreement.
"The situation in the North is becoming more serious by the week," he said, according to notes of his meeting with senior Anglo-Irish negotiators at Government Buildings in Dublin.
"The petrol bombing and attacks on police houses are particularly worrying."
Sir Kenneth said politicians were "becoming more concerned daily". He suggested: "One alternative would be to look to a long campaign of violence and attrition - doing nothing and bringing home to the unionists that this sort of action just does not pay.
"There may be arguments for this, which could be a completely logical line of action."
But he added: "On the other hand, there are arguments now for discussions, which could bring constitutional politics back into the picture again."
He went on to say: "There is much to be said for encouraging dialogues within Northern Ireland among the political parties."
Sir Kenneth was head of the Northern Ireland Civil Service at the time.
By Brian Hutton
A year after President Ronald Reagan's high-profile visit to Ballyporeen in Co Tipperary, both Irish and US officials were arguing over who should pay for unused hotel accommodation.
Confidential files revealed that major Irish groups including the Great Southern Hotels and Ryan Hotels were pressing for compensation. The claims were based on hotel bedrooms booked but not used.
Irish officials insisted that some of the cancellations were a matter for the US visiting party - and had nothing to do with the Republic.
Similarly, the Irish Department of Foreign Affairs insisted it was not responsible for profitability issues of hotels.
A memo dated April 4, 1985, indicated the Great Southern Hotel Group was told to raise the issue of 50 cancelled rooms with the US authorities.
In the case of the Galway Ryan Hotel, the department accepted "there was considerable confusion in the days leading up to the visit of President Reagan."
The Department offered an IR£7,000 compensation payment.
By Ralph Riegel
A top Irish diplomat warned the Department of Foreign Affairs in Dublin that he felt like he was "on the menu" when he had dinner with senior Tories who opposed the Anglo-Irish Agreement.
Counsellor at the Irish Embassy in London, Richard Ryan, wrote to his Department of Foreign Affairs bosses on July 30, 1986, to brief them in a top secret memo about a dinner he had with senior Conservatives.
During the dinner at Pratt's Club in London the discussion moved on to Northern Ireland.
Among those present was Ian Gow MP, a close ally of Prime Minister Margaret Thatcher, who was assassinated by the IRA in 1990.
He had resigned from Government over the Anglo-Irish Agreement.
Also present was Jonathan Aitken, who was at the time viewed as a potential future leader of the party. He was born in Dublin.
The secret briefing note was made public as part of the release of State papers in Dublin.
"Gow hosted a dinner for me at Pratt's Club where there is only one dining table around which present members sit at dinner," he wrote.
"It became quickly clear that I was pretty well included on the menu."
The diplomat said that, during a five-hour analysis of a heavily underlined copy of the Anglo-Irish Agreement, he had one friend at the table.
"One's only ally was the port decanter which one pushed around at them as fast as possible all the quicker to wear them down."
Mr Ryan stressed that the MPs were "effusive" in their praise of the Irish Government and their efforts to secure a peace deal. However, he said Mr Gow believed the Anglo-Irish Agreement was a mistake.
"He just thinks that our case is misfounded and, large as he is, he wriggles deftly from the grip when he is invited to give a counter-analysis of the best way to deal with the broad problems of an alienated minority in a State run by his friends.
"He acknowledges that his friends are not the kindliest when it comes to our own in Northern Ireland but this, of course, merely reinforces further his own integrationist beliefs."
Mr Ryan said he didn't doubt the commitment of the group towards a peaceful solution.
He added: "Overall, and again leaving Gow aside, the mood was of some scepticism but a continued preparedness to be proved wrong, allied to a blunt Saxon sense that the bottom line, when all the talking is finished, is a major breakthrough on the security front."
By Ralph Riegel
Secretary of State Tom King was "a major problem" during a critical episode in Anglo-Irish relations, a high-ranking official reported.
In a secret briefing to then Taoiseach Garret FitzGerald in January 1986, Lord King was described as "not bright", outraged by the Anglo-Irish Agreement and distrustful of Dublin.
The official Irish assessment was written up by Michael Lillis, who co-headed the Anglo-Irish Secretariat in Belfast at the time.
The fledgling peace-building institution was set up in the wake of the landmark Anglo-Irish Agreement, signed by Mr FitzGerald and Margaret Thatcher just months beforehand.
In a 13-page analysis of "some serious problems" amid an unexpectedly vociferous unionist backlash to the accord, Mr King was highlighted as one.
Mr Lillis reported to Dublin that he had been told by people very close to Mr King that he is "not bright" and "in his 'gut' opposed to, even outraged by, the Agreement" which he thought unfair to unionists.
Furthermore, the Secretary of State was convinced that British negotiators were mistaken and misled in their "estimate of the effects of the Agreement" on unionists and Mr King was also "distrustful of Dublin".
But because of a changing of senior British government figures in the region, he had become the "untrammelled supremo on the British side" and as such would set the pace of the Agreement's implementation.
This was causing problems for Dublin, who wanted to reforms made quickly and clearly.
Mr King, at the time, believed progress should be more subtle in the face of a growing revolt.
In a clearly pessimistic view of him, Mr Lillis suggested the only positive factor about the Secretary of State was that his appointment was a "demotion" and so his "last chance to restore his career" which effectively meant making a success out of the Agreement.
By Ralph Riegel
A former leader of the Presbyterian Church in Ireland encouraged his children to move away from Northern Ireland because he believed Britain would eventually pull out, according to released state papers.
Rev John Dunlop, a north Belfast minister known for his cross-community peace-building and who went on to become Moderator of the church, met an Irish government official at his home in December 1986. Notes of the meeting show Rev Dunlop "speculated that, in the longer term, the British Government would decide for financial reasons to withdraw from Northern Ireland".
"Already quite a few unionists (including himself) were advising their children to seek employment not in Northern Ireland but in Britain."
By Brian Hutton