It is now well documented that Margaret Thatcher came to regret the Anglo Irish Agreement, which some of her officials and senior cabinet colleagues put pressure on her to sign in 1985.
That she succumbed to this pressure has had consequences ever since for the constitutional integrity of the United Kingdom. Dublin is so confident that it has a say in the running of Northern Ireland it is currently helping to make the return of direct rule more difficult.
One thing that the then prime minister came to see quickly was that the supposed co-operation from Dublin on security measures to tackle terror never came through.
Of course it did not.
Many people died, particularly in border areas, at the hands of IRA murderers as a result of that failure – specifically the failure to extradite them.
It now transpires that Mrs Thatcher conveyed her frustration to Charles Haughey, the then Taoiseach, at a meeting in December 1987. It was a month after the IRA Enniskillen massacre of 11 Protestants at a Remembrance Sunday service in the town. This was, another cabinet paper shows, seen by Mrs Thatcher as a final straw in Dublin’s security failures.
It seems, from the note, that Mr Haughey tried to persuade her that the situation would improve. Shamefully it didn’t and there has never been anything that suggests it would have done, so long as the Provisional campaign continued.
Now the British state is being carefully scrutinised for its role in the Troubles, while very little heat is being put on the IRA.
Sinn Fein is so comfortable with the coming legacy structures, agreed in the Stormont House Agreement, that it is demanding their implementation.
If, however, there is to be a fair resolution of legacy then the IRA campaign will have to be scrutinised pro rata in funding, per death, with any legacy inquests into state killings.
And if the past is going to be examined carefully, then Dublin’s abject failure to help stop the IRA will need scrutiny too.