Northern Ireland was an embarrassing irritant for Margaret Thatcher, distracting her all too often from her grand design of reforming Britain internally and restoring it as a world power.

No matter how decisive she proved to be in facing down the trade unions, or doing the same to the Argentinians in the Falklands, she was stymied in Belfast and Dublin. She had little or no room for manoeuvre whether she was dealing with the IRA hunger strike or the Anglo-Irish agreement. Any deal was anathema to one side or the other. As a result, Margaret Thatcher could never hope to achieve in the 1980s any of what we have now in 2012.

Looking back I have some sympathy for her. Though she did escape death at Brighton's Grand Hotel, she was still a Prime Minister in the wrong place at the wrong time.

I met her Secretaries of State, Humphrey Atkins, James Prior, Tom King, Douglas Hurd and Peter Brooke, for briefings and over lunch or dinner at Stormont Castle. Like their formidable boss in Downing St, they were imprisoned by the intransigence they encountered here.

Thatcher was constantly charging her ministers and officials in Belfast with finding solutions to fit her three strand strategy to isolate if not defeat the IRA. She had little faith that any of their grandiose plans would succeed and they didn't.

Every initiative foundered on the unwillingness of either nationalists or unionists or sometimes both to agree. Dublin was duplicitous. Charles Haughey charmed her and Garret FitzGerald annoyed her with his woolly ideas but neither convinced her that the Irish government meant what it said about security co-operation.

The Catholic Church offered no solace to her. Of Cardinal Tomas O'Fiaich she said "he was a romantic republican whose nationalism seemed to prevail over his Christian duty of offering unqualified resistance to terrorism and murder".

Out of 900 pages in her memoirs, Thatcher devotes only 40 pages to Northern Ireland, a telling statistic in itself. Time and again, her exasperation shows through her recollections.

She distrusted the Irish Government's promises on security, saw the SDLP as weak-willed and capitulating to Sinn Fein, and considered unionists ungrateful for her commitment to keeping Northern Ireland as an integral part of the UK. Hindsight suggests she was impatient and even bored with the intractability of the problems confronting her in Belfast.

For example, she did not involve herself enough in drafting a joint statement with Charles Haughey which said they would devote their next meeting "to special consideration of the totality of relationship within these islands". Long before anyone had dreamed up the Anglo-Irish agreement, Haughey briefed journalists on a major constitutional breakthrough to which she had not agreed and which left her to deal with outraged unionists.

Thatcher's strategy to wean the IRA away from the general Catholic population by finding some means of ensuring the latter acquiesced to Northern Ireland's constitutional framework was a forlorn hope at the time. She sought to deprive the IRA of international support from Libya or Irish-Americans. She wanted closer cooperation with the Irish Republic, but really only because she saw the south as too safe a haven for IRA terrorism.

Her problem from the outset was that the IRA was tipping everyone over the brink with its "Armalite in one hand, ballot box in the other" strategy. Political trust was non-existent. A security solution alone was unrealistic.

Her term of office was punctuated with some of the worst atrocities. She was at Chequers on the August bank holiday in 1979 when she learnt of Lord Mountbatten's murder and the killings of 18 soldiers at Warrenpoint. The IRA's bombings at Enniskillen, Harrods, Hyde Park, Regent's Park, Deal, Ballygawley, and Brighton focused her thoughts.

Had she caved in to the hunger strikers, she would have alienated even the most moderate unionist. Like her predecessors, she believed it was better to keep the unionists onside and hope moderate nationalists would eventually join them.

In the end, Margaret Thatcher got nowhere because no one was prepared to play ball with her. For all her national and international achievements she stands accused of making things worse on this side of the Irish Sea. In her time she united nationalist Ireland over the hunger strikes and unionist Ulster to say No to the Anglo-Irish agreement.

The truth is that Northern Ireland was not ready for peace. Margaret Thatcher found to her cost that each side thought it could still win. That was not her fault. It was ours.