By that stage, as well as intensified efforts with the Dublin government, a backchannel was already in operation between the UK Government and Sinn Fein.

Secret negotiations between Gerry Adams, its leader, and John Hume, head of the moderate nationalist SDLP, had started in 1986.

Insight into Britain and Ireland’s views on the crisis

The documents released on Tuesday in Ireland provide a picture of an increasingly candid relationship between the two administrations.

In June 1991 Charlie Haughey, Mr Reynold’s predecessor, had told Sir John that they needed to take the issue “by the scruff of the neck”, rather than rely on the political parties in Ulster.

He also told Sir John: “There are great benefits for both of us in the world from a clearing of the decks. Both countries could then settle down to some sort of normal relations. I hope in all this I am not teaching my grandmother to suck eggs.”

Responding to concerns from his British counterpart about keeping the Unionists in Northern Ireland on board with negotiations, Mr Haughey said: “Don’t attribute too much sophistication and understanding to the unionists. If the British Government says: ‘This is the way we must go,’ they have no alternative.”

Sir John responded that any proposals had to be “broadly accepted by the unionists and also by Parliament”.

In 1993, Mr Reynolds and Sir John signed the Downing Street Declaration. A landmark moment in the peace process, it recognised that Ulster was free to join the Irish republic, but only with the democratic consent of the majority. It was to be the foundation stone for the 1998 Good Friday Agreement.  

That year, Sir John also authorised an intensification of secret talks with Martin McGuinness, Sinn Fein’s chief negotiator, and persevered despite the murder of two young boys in the Warrington bombing.   

In 1994, the IRA signed a comprehensive ceasefire which, while broken in 1996, was a major step towards the group’s permanent disarmament in 2005.

Lord Butler, Cabinet Secretary to both Sir John and Tony Blair, said in 2007 that the Tory prime minister took more risks than his successor and deserved greater praise for laying the groundwork for peace in defiance of those in his Cabinet, who argued that the IRA could not be trusted.

However, in his February 1992 conversation with Mr Reynolds, Sir John appeared to reveal his own doubts about IRA good faith. 

“You know that more bombs are threatened in Whitehall. If they are serious, they are certainly going the wrong way about it,” he told the taoiseach.

“Before a cessation of violence, they always become more active. They always like it to appear that if a ceasefire comes about, then they have not acted from weakness,” Mr Reynolds told Sir John in response.

The extent to which the Provisional IRA were brought to the negotiating table by British military and security efforts remains a point of deep contention.