1986 State papers: Thatcher said UK got North Border 'wrong' in 1921
British prime minister Margaret Thatcher admitted to Irish officials the UK "got it wrong in 1921" with the North's border.
A series of extraordinary admissions between Mrs Thatcher and then Taoiseach Dr Garret FitzGerald have emerged from the 1986 archives released under the 30-year rule.
Both leaders were in close contact throughout 1986 as the UK and Ireland attempted to stand behind the Anglo-Irish Agreement amid furious unionist and loyalist opposition to the deal.
The duo met on December 6, 1986, in London - and Mrs Thatcher made a series of blunt admissions in assessing the security situation along the Border.
"You (the Republic) haven't the resources to maintain protection on the other side of the Border," she said.
"I do feel very depressed at times about the whole situation. The violence has not been defeated. The SDLP have not done what we are expecting them to do.
"However, it is Christmas - and I had better stop feeling depressed."
Dr FitzGerald praised the RUC for the work it had done in co-operating with gardaí and pressed for all UDR patrols to be accompanied by the RUC.
But he warned: "Both forces have a next-to-impossible Border to watch."
Mrs Thatcher bluntly admitted: "Yes, we got it wrong in 1921."
The meeting concluded with one Irish civil servant noting: "The prime minister then went on…including a rather wistful reference to whether she could continue, in all seriousness, to send young men to their death in Northern Ireland."
Both governments expressed their repeated concerns about the security situation in the North given the upsurge in unionist and loyalist protests and demonstrations over the Anglo-Irish deal.
Mrs Thatcher warned that such a reaction was "negative and very dangerous".
"The Unionists are saying they have lost everything and have got nothing," she said.
One briefing note warned that RUC chief constable John Hermon was "genuinely frightened" by the implications of one demonstration at Hillsborough.
Another briefing note warned: "Dublin has not grasped the fundamental reality that Northern Ireland is and will remain ungovernable."
There was also concern in both governments over Libyan arms reaching the IRA.