During the framing of the historic Anglo-Irish Agreement of November 1985, Garret FitzGerald took the opportunity of a joint meeting in Lisbon to compare notes with the British foreign secretary Geoffrey Howe.

He appreciated that Howe had a deeper understanding of what was at stake in the proposed agreement than had his prime minister Margaret Thatcher.

After their meeting, FitzGerald noted Howe's emphasis on "the magnitude" of what was already in the draft agreement, "conceding to us a right of involvement" in Northern Ireland, which the taoiseach said the British minister sincerely believed "would be the start of an evolving situation of historic significance".

Such an outlook was shared by many of the players on the British side: by their chief negotiators, Robert Armstrong and David Goodall, by Alan Goodison, their ambassador in Dublin, by arts minister, Lord Gowrie, and by attorney general Michael Havers.

Thatcher herself was a wobbler and feared that she was being bounced into the agreement – which in many respects she was. She was also a chameleon, impressed by the most recent assertive voice she had heard. Northern Ireland secretary Douglas Hurd was lukewarm and inclined to be minimalist if not negative about the ongoing negotiations.

The Milan summit at the end of June would be Thatcher’s last face-to-face meeting with FitzGerald before they met to sign the agreement at Hillsborough in November. Just before this Milan meeting, Armstrong had advised Dublin that each time FitzGerald and Thatcher met, she emerged newly energised on the problem.

Foreboding and pessimism

A month after the Milan summit – and despite many significant clauses yet to be agreed – the British cabinet approved the draft agreement.

Armstrong began immediately to press on with preparing for the signing ceremony. He sent Thatcher a draft communique, but many of its provisions “astounded” her. Indeed, she scolded that “the tone is wrong”.

And there would be a further barrier two months later when Tom King, replacing Hurd as Northern Ireland secretary, sent her his response after reading the files for the first time. He reckoned that the Irish were getting "an unprecedented foothold in the internal affairs of the United Kingdom". His letter amounted to a vote of no confidence in the British negotiators.

Again she hesitated but was persuaded to proceed by Howe and Armstrong and the agreement was duly signed at Hillsborough Castle on November 15th, 1985.

Within weeks Thatcher and FitzGerald would meet again in the margins of a European Council. They had no more than 30 minutes at Luxembourg on the morning of December 3rd.

From all accounts, it was far from a celebratory meeting.

“You have all the glory. We have all the problems,” Thatcher opened.

Unionist reaction had been “much worse than expected”, she said.

FitzGerald insisted they could not allow “threats or menaces” to throw them off course.

Thatcher appealed for gestures to appease the unionists. She was especially apprehensive about their fury if FitzGerald got his way and the Irish civil servants who would manage Dublin’s future role would be based in the citadel of Stormont itself. She had “got to reassure the unionists and fast”.

They had been acting constitutionally up to this. But, she wondered, might there now “be strikes or violence”?

‘Dynamite’

Despite her foreboding and pessimism, FitzGerald ventured to suggest the introduction of something that had been discussed by the officials during the negotiations: early release from prison of IRA offenders as a confidence-building measure, were there to be “a sustained period of reduced violence after the agreement”.

Thatcher expressed no interest. “That would be dynamite – no, not dynamite, nuclear.” She could not contemplate the release of people “guilty of bombing, of murder and other atrocities”.

FitzGerald countered that further support could be won for the SDLP “if we can work on the families” of IRA prisoners. He advised Thatcher that “the unionism of the unionists” was the best card she could play.

“But what is it leading them to?” she asked, rhetorically. “It is leading them to something different from the union.”

There were further indecisive exchanges before Thatcher, noting that it was five past nine, suggested that European business called.

Michael Lillis, as head of the Anglo-Irish section in the department of foreign affairs, continued to monitor opinion.

Irish ambassador to London Noel Dorr informed him of a letter received from Sir Robert Andrew of the Northern Ireland Office indicating that their contribution to the making of the agreement had been largely overlooked in the media.

Not that Andrew was other than “entirely happy” with this omission, as he believed it was “not healthy” at the moment to be identified as one of the “quislings” who had taken part in what was seen by unionists as an “act of treachery”.

That unionists had not been properly briefed about the negotiating process was a substantial criticism. And Thatcher was sensitive to the charge of being duplicitous and a traitor. But her biographer Charles Moore suggests that her reluctance to talk to the unionists "partly stemmed from her surprisingly strong dislike of unpleasant scenes".

All the insiders well appreciated how the unionists, and DUP leader Ian Paisley in particular, would have used any briefing to attempt to scupper the embryonic agreement.

From the Irish side, Lillis had suggested that, even if the British had assured Paisley the agreement was concerned with no more than “increasing the teaching of Irish in the Glens of Antrim”, he would have rushed from the meeting with “talk of betrayal”.

After its signing, Paisley denounced Thatcher from all his pulpits: from the gates of Hillsborough Castle before the signatures were dry; from a mass rally in Belfast city centre which launched the slogan, “Ulster Says No!”; at the Westminster debate on the agreement; and from the pulpit in his Free Presbyterian Church, when he invited God “in wrath” to “take vengeance upon this wicked, treacherous, lying woman”.

Trump card

The Irish, who had been pestering the British to concede what were called confidence-building measures – and annoying London by calling them the CBMs – had now discovered their trump card.

Ironically, it was Paisley’s anger which provided the greatest CBM of all. If Paisley disliked the Anglo-Irish Agreement this much, then even the most cynical Northern nationalists reckoned there must be something in it.