The island of Ireland is not “ready” for a unification referendum and calls to have one quickly are “an overstretch”, former tánaiste and minister for foreign affairs Dick Spring has told a Belfast conference.

Speaking at a Queen’s University Belfast gathering to mark the 40th anniversary of the Anglo-Irish Agreement in 1985, Mr Spring urged political leaders of today “to jump one fence at a time”.

“The most remarkable thing that has happened is that the guns are silenced. Let’s take that as a huge achievement. The guns are silenced and people are into democratic politics. Let us make Northern Ireland work.

“Let us develop relationships with the South, economic relationships in particular. We can benefit, North and South can benefit tremendously co-operating on economic matters. But let’s not try to overstretch.

“I don’t think that we’re ready for a referendum [on unification], or for debates. There’s an awful lot of work to be done. It’s a long way away,” Mr Spring said.

His declaration comes just days after Northern Ireland Secretary of State, Hilary Benn said a border poll is “way off in the distance”, because no one is “arguing that there is an appetite for constitutional change”.

The Queen’s conference was well attended, including by diplomats who played a key role in the negotiation of the 1985 agreement, notably retired foreign affairs officials, Michael Lillis, Noel Dorr and Sean Donlon.

Highlighting the importance of the agreement signed on November 15th, 1985, Mr Spring said it gave Dublin a voice in Northern Ireland’s affairs for the first time – something denied for years by London.

Praising Fine Gael’s Garret FitzGerald, Mr Spring went on: “I will forever say that it probably couldn’t have happened without Garret. He had huge powers of persuasion with Margaret Thatcher. She was very reluctant.”

Primarily seeking greater help from Dublin against the IRA, Mrs Thatcher had “some very funny ideas”, he went on, believing that Catholics and Protestants could be forcibly moved to different counties within Northern Ireland.

“Somebody mentioned Cromwell in the conversation … that that had been done before, not very successfully,” said the former leader of the Labour Party: “Ultimately, I think, it was Garret’s persuasion all the way.”

One of the agreement’s key architects, former foreign affairs official Michael Lillis, spoke of his early contacts with a leading British official, the late David Goodall.

During a famous stroll along the Grand Canal in 1983, Mr Lillis proposed that gardaí and Irish soldiers, along with judges from the Republic should operate in Northern Ireland to give nationalists confidence.

His ideas were seen as “crazy” by London, he said, but they were designed “to wake the British up” because they did not want to hear anything from Dublin: “So, you had to present them with something which was a bit shocking, and I did that deliberately.”

Explaining how US president Ronald Reagan’s support was gained, Mr Lillis’s colleague, Sean Donlon told of how he secretly briefed three people in Washington, including House speaker Thomas Phillip “Tip” O’Neill and Democratic senator Ted Kennedy.

However, the third crucial person is little known here, a Republican called Bill Clark who was “an old friend of Reagan’s from the Californian days”.

He was deeply interested in Ireland, even though he had “absolutely” no Irish blood, but had spent his honeymoon in Monaghan with his German wife.

That “gave him roots in Ireland”, said Mr Donlon. Later, he bought a house in Malahide, kept horses in Ireland and had a private aeroplane in Dublin Airport.