In public, Margaret Thatcher was the Iron Lady, a rock-like symbol of certitude who, as far as Northern Ireland was concerned, elevated security considerations and, in particular, standing up to the IRA above all other factors.
Yet, as the 30-year state papers now indicate, there was a private aspect to her, in that she was prepared to kick around ideas, like re-partition, whose disclosure would have astounded much of the world.
The thing was, however, that most such ideas were only fleetingly considered before being discarded.
Her technique was once described by Sir David Goodall, the Foreign Office diplomat who went on to become one of the architects of the 1985 Anglo-Irish Agreement. "Her way of teasing out a problem was to throw out various outrageous suggestions," he said.
After one session involving the two prime ministers at Chequers, she called her officials in for a whisky and what he described as "a fair knockabout".
According to Sir David, she threw out the question: "If the northern population want to be in the south, why don't they move over there? The Irish are quite used to movements of population." The precedent she pointed to was that of Cromwell.
But, although the idea of re-partition was never publicly aired as a policy option, it was a recurring private theme with her.
In fact, it had been briefly considered, along with a variety of other options, by her predecessor, Edward Heath. During a period of early-1970s turmoil, he had officials examine the idea of dividing Northern Ireland into Protestant and Catholic districts, with the latter being allowed to join the Republic.
Senior Thatcher aide Charles Powell explained its attractions for her: "For Mrs Thatcher, security was paramount and she many times came back to this. She said, 'Couldn't we redraw the border to at least make it more defensible?'
"Indeed, at various times, she even speculated on the possibility of population movement, though it very quickly became apparent this was not a politically feasible task. Now and again, she got the Ministry of Defence to do various studies of this, but it never worked out.
"She thought that, if we had a straight-line border – not one with all those kinks and wiggles in it – it would be easier to defend. But the military always came back and said no, it would simply be too difficult."
So it appears to have been the generals who talked Mrs Thatcher out of it. It is easy to imagine why, since even the most ingenious recasting of the border would have left the nationalists and republicans of west Belfast within Northern Ireland.
Thus, the Army would have been left with the task of keeping the Belfast IRA penned up, while keeping open a corridor to the Republic and holding marauding loyalists at bay. The net effect is likely to have been a much worse security situation.
Although military assessments may have been decisive in Mrs Thatcher's abandonment of re-partition, many other factors would have ruled it out after the most cursory examination.
The civil service analysis was couched in carefully measured and respectful terms, yet it is not difficult to detect that officials were absolutely horrified at the implications and practicalities of the idea.
In fact, it is entirely possible that any such move could have led to a major political and security deterioration, introducing huge new instabilities into an already unstable situation.
Although Mrs Thatcher appears unaware of it, the transfer of territory from the UK to the south would have been viewed as a victory for the IRA and one which would have encouraged it to fight on.
At the same time, as the civil service response pointed out, much of the unionist population would have regarded a handover of land to the Republic as a victory for terrorism and a betrayal of historic proportions.
The prime minister might have viewed it as a daring and dramatic new anti-IRA security measure, but many Protestants would have viewed it as a major defeat.
Loyalist paramilitary groups would surely have expanded in response to Protestant anger and fears that such a handover would be the first of a series leading to the eventual disappearance of Northern Ireland.
And, in addition to these considerations, there would have been the sight of large-scale population movements of a type which, in other parts of the world, have led to generations of deep bitterness.
Nationalists as well as unionists would have been alarmed at the idea of big changes to the border. One of the deepest instincts of southern politicians was always to protect their state from a spillover of the Troubles: any move to have the Republic absorb tens of thousands of northerners would have caused utter consternation in Dublin.
In other words, redrawing the border could easily have led to a crisis of potentially Bosnian proportions. In fact, once the military had advised her to forget the whole thing, it is difficult to see why she would return to it.
The Troubles were lethal, long-lasting and disastrous: it is a sobering thought that some ill- advised moves, such as this one, could have made them last even longer and cost even more lives.