Gardai help to combat IRA operations on mainland UK
A small group of gardai had "excellent relations" with the Metropolitan Police in London at the height of the Troubles - without the knowledge of some government ministers - which helped combat republican terrorist activities on the mainland UK.
A 1985 paper from within the British government, which assessed the Irish attitude to security co-operation, described how the small number of officers helped despite the political sensitivity of dealing with the British at the time.
The close relationship between the gardai from the intelligence and security branch and the Metropolitan Police in London came at a time when relations between the higher levels of the gardai and their corresponding numbers in the RUC were chilled and distrustful.
The briefing document details how security was a politically sensitive area for the Irish government at the time when it wanted to avoid being seen as working in favour of the British presence in Northern Ireland.
"Because Republican terrorists are genuinely careful not to directly threaten Irish government interests, and because of the political importance to the Irish government of upholding nationalist aspirations in Northern Ireland, and not appearing subservient to British government interests, the Irish government perceives significant political constraints on the extent to which it can act further against republican terrorists," said the document.
However, close relationships were developed between a small band of gardai and the Metropolitan Police at a level which was not known by some members of the cabinet.
"This is achieved by working with a small number of garda officers who, although sensitive to the political constraints, and to the potential hostility of some of their colleagues, are nevertheless prepared to be extremely helpful and whose attitude gives no indication that they are anything other than whole-heartedly dedicated to the defeat of terrorism from whatever source."
The close collaboration had resulted in the IRA campaign on the mainland UK being disrupted, in one instance by an arms dump being discovered in 1984.
The spend on security at the time was more in Ireland per head of population than in the UK but the 50 intelligence and security branch officers - from a total of 350 - outside of Dublin could not maintain an effective presence on the border, according to the briefing.