State Papers released by the National Archives under the 30-year rule today, show that British Prime Minister Margaret Thatcher told Taoiseach Garret FitzGerald that she felt "very depressed at times" about Northern Ireland as "the violence had not been defeated".
In a meeting before Christmas 1986, Mrs Thatcher confided in Mr FitzGerald that she was "depressed" as the year after the Anglo-Irish Agreement proved difficult.
The papers also reveal details of a Libyan plot to kill the British prime minister and her family.
95 years since the signing of the Anglo-Irish Treaty, the State Papers also reveal that Mrs Thatcher told Mr FitzGerald that Britain "got it wrong in 1921".
Mrs Thatcher's comments came during a meeting with the Taoiseach in London in December 1986.
She accused the Irish government of being unable to protect the border.
Previously secret information has also come to light about a senior Libyan official telling an Irish diplomat the Gaddafi regime in Tripoli wanted to fund the IRA to the tune of 50 million dollars, and kill Margaret Thatcher and her family.
Briefing documents prepared for the Irish government also show that under Gerry Adams' influence the IRA decided it should lie low and until the Anglo-Irish Agreement "fell apart of its own accord".
We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences