David McKittrick: The segregation that still pervades Northern Ireland

Edward Heath's thought of re-partitioning Northern Ireland 30 years ago by forcibly relocating half a million people – a third of its population – is still striking enough to cause a gasp of horror. The scenario of British troops enforcing large-scale ethnic cleansing, against a background of furious communal violence, is nightmarish.

The papers just released by the Public Record Office include freehand drawings of a redesigned state. The little sketches look inoffensive enough, but if enacted they would have produced a society in conflagration: there could have been thousands of deaths, grabs for territory, massacres.

Mr Heath grasped this perfectly well, but he was desperately thrashing about for contingency plans. After Bloody Sunday he wrote: "I feared that we might, for the first time, be on the threshold of complete anarchy."

The plans, of course, were never acted on, Mr Heath concluding they would be a disastrous mistake. They were in any event very much designed for the most extreme of emergencies, and things never got quite that bad. They remain, however, a stark reminder of how dangerous things looked back then, and how far Northern Ireland has since travelled.

The doodlings of British politicians on maps of Ireland have often produced unhappy results. They led, for example, to the creation of Northern Ireland itself, which has been such a troubled and unstable entity. Nor was Mr Heath the last Prime Minister to toy with the idea of redrawing boundaries: Margaret Thatcher did it too, as her private secretary, Charles Powell, recalled for the Endgame in Ireland television series.

"Now and again she got the Ministry of Defence to do various studies of this," he remembered. "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 it never worked out."

One of the few things that Mr Heath and Mrs Thatcher had in common was their willingness to experiment in Ireland. Both maintained clandestine contact with the IRA and both attempted military solutions; both strongly clashed with Dublin before ending up with Anglo-Irish strategies and a commitment to negotiation.

Yet, since the Heath years, increased segregation and a kind of re-partition has been happening steadily, not at the point of British bayonets but on a voluntary basis. The increased Catholic and nationalist population is now in confident control of the largely rural west, and Belfast has a Sinn Fein Lord Mayor. The falling Protestant population has congregated more and more in the east: it almost looks as though it is huddling there.

None of this makes formal re-partition any more conceivable as an option, if only because the city of Belfast contains some 130,000 Catholics. But it does make the point that many people have a little frontier within their minds, built in to their political perspective.

The idea of political structures that might include people such as Sinn Fein and the IRA, and violent loyalists, was not to fully take root until the 1990s. Yet even in 1972, when almost 500 people died, Mr Heath was prepared to sanction talks with the IRA, the cabinet papers disclosing a senior official's view that Gerry Adams undoubtedly desired "a permanent end to violence".

The IRA demands of the time for British withdrawal could not be met by the Heath government or indeed any subsequent administration. In the 30 intervening years, however, most elements have lowered their sights, which made possible the emergence of the peace process. One of the foundations of this process is that segregation, in terms of both political tradition and where people live, is an unfortunate but inescapable fact of life.

Thus politicians in the Belfast Assembly must, as almost their first act after election, state whether they are Unionist or nationalist. Many do not like this, but it is sadly accepted that it is best to acknowledge the existence of such a deeply divided society.

The central question for the new year is whether that Assembly, which is presently suspended, can be resurrected in the wake of a new deal in which the IRA winds up most or all of its more unsavoury activities. To that end, intensive negotiations are expected in February.

As things hot up, these will doubtless be described as a crisis, yet it is instructive to compare what is at stake now with what Mr Heath faced in 1972. The 500 deaths of that year compare to a dozen last year: the IRA killed 235 people in 1972, but just two last year, while the loyalist death toll fell from 121 to 8.

Last year's events seem almost petty in comparison to 1972's convulsions. The Assembly was suspended, yet nobody feared, as Mr Heath did 30 years earlier, that "complete anarchy" might result. Instead, the sense is that there is a good chance of the Assembly being revived. In its short lifetime its politicians showed little sign of developing warm friendships, but they give the impression of believing it provided a level playing-field.

Partition may still exist in men's minds, and life in Northern Ireland will, in all likelihood, continue to be punctuated by acts of violence. Yet the sense that events could spin out of control has just about disappeared. More drama certainly lies ahead, but the fear of anarchy seems to have gone.