Margaret Thatcher believed the Anglo-Irish Agreement gave the Irish government all the glory and none of the problems, State papers have revealed.
The prime minister's anxieties were laid bare a fortnight after the signing of the historic treaty during a head to head with taoiseach Garret FitzGerald on how to win unionist support, and fast.
In a half hour meeting in the Kirchberg Building in Luxembourg on December 3 1985, the British PM said she was deeply upset with accusations she faced of betrayal and treachery over her handling of Northern Ireland affairs.
"I am very worried about developments. You have all the glory. We have all the problems," she told Mr FitzGerald.
Documents released by the National Archives in Dublin under the 30 year rule show the taoiseach urged Mrs Thatcher to stick with the treaty despite the much deeper than anticipated Unionist opposition.
At the same time, she pressured him to get visible evidence of beefed up border security on the Republic's side.
"The Unionist reaction is very much more serious than I had thought," Mrs Thatcher said.
"I have been told: you are treacherous, you have betrayed us, etc. I have got to reassure the Unionists and fast."
Mrs Thatcher told the taoiseach that unionists had to be involved in some way in the workings of the treaty after advisers warned Ian Paisley and Jim Molyneaux were only articulating the "popular feeling" on the ground.
It was one of the rare occasions when emotion can be detected in the confidential notes in State papers and in the late Tory leader's mind.
"I am deeply upset about the betrayal charges," she said.
"The trouble is they (unionists) will hear only what they want to hear. There is no good saying things in an English voice. Irish voices must come in and help.
"The unionists are saying that there are no visible results. I have been only too relieved that they reacted constitutionally. There have been no strikes and no bombs."
Mr FitzGerald urged the PM not to be deflected by menace or threats and tried to get her to focus on the options to bring unionism on board.
His calm, methodical approach in the face of a feared breakdown in law and order is striking when set against his views on Mrs Thatcher which were recorded in other documents from his office.
When he first met her as opposition leader in the Commons, Mr FitzGerald immediately felt he could do business with her one day.
In a meeting with the SDLP, he reflected how:"It had been clear to him that if he could turn her", she had the qualities necessary to do something serious about the North. He thought the Tory Party could carry the situation under her leadership.
He had made up his mind when he met her to make a major effort to have some influence over her.
Mr FitzGerald used the Luxembourg summit to raise the prospect of getting early release and remission for Maze prisoners if a few months of relative peace followed the signing of the treaty.
Mrs Thatcher totally rejected the idea, saying: "That would be dynamite - no, not dynamite, nuclear. We could not think of relief for people guilty of bombing, or murder and other atrocities."
The Tory leader had been left reeling with the resignation of her parliamentary secretary Ian Gow and warnings of MPs going to Northern Ireland to campaign for unionists in the upcoming local elections.
Another option put out was to get the SDLP to speak out in support of the treaty, and nine days later the party was preparing a statement urging people not to react impetuously.
In an emotional dinner meeting with the taoiseach, John Hume and Seamus Mallon were set to herald it as an opportunity for progress towards peace and stability.
The taoiseach told them: "What has emerged is far short of what our aspirations would require for fulfilment. It is a small step. The Government realises that it is taking a considerable risk as is of course the SDLP.
Mr FitzGerald said the Anglo-Irish Agreement had potential to go far beyond its present state, and while he was not sure if it was right to call it historic, he said: "Anything that could possibly bring peace was worth trying."
Mr Mallon described it as one of the most moving moments he had experienced and the SDLP would not be found wanting.