One substantive achievement still adheres to Tony Blair's otherwise threadbare legacy: peace in Northern Ireland. In May 2007, a new power-sharing government was sworn in at Stormont, dominated by the apparent historic irreconcilables Ian Paisley and Martin McGuinness. However unsatisfactory the province's polity is today, it seems unlikely that wholesale terrorism will resume; this, after decades in which the highest aspiration of British governments was “an acceptable level of violence”.

The man who did much of the work that culminated in the 2007 settlement was Downing Street's chief of staff, former diplomat Jonathan Powell. He has now written a book telling the story of how it was done. He describes years of commuting across the Irish Sea, sometimes with his master, often alone, and hours spent at sordid Belfast secret rendezvous, communing with some of the more ghastly inhabitants of the planet. There was also an awkward day at Downing Street in 1998, when Powell spotted Gerry Adams and McGuinness playing with the Blair children in the Downing Street rose garden. Terrified that they would be photographed, he hastened to shepherd them indoors.

Those of us who were eyewitnesses of the early years of the Troubles find it hard to shed the baggage of our memories. Blair and his people, drawn from a different generation, sought to wipe the slate. Powell writes: “It is very hard for democratic governments to admit to talking to terrorist groups while those groups are still killing innocent people. But on the basis of my experience I think it is always right to talk to your enemy, however badly he is behaving.”

This must be so. Powell could never have sustained a dialogue with Sinn Fein had he walked into meetings mindful of Adams's and McGuinness's pasts as career murderers, or allowed his behaviour towards Paisley to be coloured by awareness of his record as one of the begetters of Ulster's tragedy. The Downing Street negotiators simply talked to such men day after day, month after month and year after year as if they were sensible folk who wanted a better future for their society than its past - and ultimately this worked.

Powell risked a little black joke to Sinn Fein, that when he offered to get rid of Irish prime minister Bertie Ahern, he did not mean the Ballymurphy way. Adams gave Tony Blair a tiny harp of bog oak, growling that this was the only bit of Ireland he could keep. One of the loyalist negotiators wheedled out of the prime minister the revelation that Cherie's expected baby would be a boy, whom they would call Leo. The Ulsterman later boasted to Powell that he had made a packet by placing a bet on the name with his bookmaker. What a crew.

Powell's account will be invaluable to historians, but I fear that most readers will find it as wearisome as did the principals their decade of wrangling. The dreariness of the tale stems from the fact that it recounts a cycle endlessly repeated: suggestions from London; rejection by Sinn Fein: wheedling by Powell or Blair; enraged intransigence from the Unionists; temporising from Adams; intercession by the Dublin government; more stonewalling by Sinn Fein; an eventual inch or two of progress.

I paraphrase only slightly. The Unionists, and several Northern Ireland secretaries, came to believe that Powell had succumbed to Stockholm syndrome[] - the hostage falling in love with his captors, or at least the Downing Street official forging an over-intimate relationship with bloodstained terrorists. Powell argues, convincingly, that what the prime minister and he got right in Northern Ireland, and has always been missing between Israel and the Palestinians, is a dogged commitment to sustaining a process. “You have to keep the process moving forward, however slowly. Never let it fall over.”

Powell's descriptions of negotiations - “having learned the skill of creative vagueness from my boss” - are enlivened by piquant asides about the Blair government. One Northern Ireland secretary grew regally petulant when he felt marginalised in negotiations, then tearful when forced to resignation by his dabblings with the Hinduja[] brothers' passports. Dear Peter, as in Mandelson[], was lucky not to be strangled by exasperated colleagues, instead of being bought a ticket for the Brussels gravy train as EU commissioner. Tony shook his head to Jonathan one day, saying how pompous Peter had become. Powell, while paying tribute to Mandelson's political skills, writes: “He would have been his own worst enemy, if he had not created so many even worse enemies along the way.”

Powell writes tetchily about a distraction in mid- 2006: “We in No 10 had to waste a good deal of time in the summer with the beginnings of [commander] John Yates[]'s investigations into the ‘cash for peerages' drama.” So irksome for statesmen, is it not, to be obliged to explain their squalid machinations to the boys in blue? He fires another squib at the head of the army, General Sir Richard Dannatt[], for wasting more of Downing Street's valuable time with his November 2006 admission to the media that he hoped British troops could leave Iraq sooner rather than later.

The self-righteousness that enfolded even Blair's most disastrous errors is woven deep into this tale. Powell describes how his commitment to the Ulster negotiation cost him missed children's birthdays, a foreshortened parting with a dying mother, interrupted weekends and holidays - as if deprivations of this sort are not the price of power in any walk of life. Come off it, mate. You were principal acolyte in a premiership that ended in moral bankruptcy.

Powell offers a mumbled admission - “£200m could have been spent on better things” - that the 1998 decision to launch Lord Saville's inquiry into Bloody Sunday[] was mistaken. It was all Mo's idea, apparently. Powell treats Mowlam[] with kid gloves, as befits the memory of a new Labour icon. Yet the best that can be said of her tenure as Northern Ireland secretary is that her shameless vulgarity made it plain to the Northern Irish that she was not merely another English toff sent to stitch them up. Mowlam properly belonged in the cast of a TV sitcom rather than a cabinet post.

Powell says in his preface that “for me, the heroes of this story are Tony Blair, Bertie Ahern and the party leaders in Northern Ireland”. Yet my substantial reservation about this book is that, while it provides a detailed and probably reliable account of what Blair and Powell did, it says next to nothing about context. The author does acknowledge that 9/11 blew away American support for the IRA, doing more to discredit Republican terrorism than British governments had contrived in 30 years. But he pays only lip service to the economic issue, which some of us regard as pivotal.

Until the 1980s, the Irish Republic was a wretchedly poor and ineffectual little country. When I lived in Co Kilkenny[] in the late 1970s, I often drove for four hours to Northern Ireland to phone Britain, because communications down south were a joke. For decades, northern Protestants had nothing to gain from engagement with the south. Today, that picture is transformed. A united Ireland would vastly profit Ulster, and its more intelligent citizens know this. To be sure, Protestant extremists still bang their drums and win elections. But the critical factor in making the 2007 agreement possible was not the genius of Blair or a damascene conversion to virtue by a generation of Irish fanatics. It was the transformation of the economic and social circumstances of the entire island, the rise of the “Celtic tiger”.

Yet it is not in doubt that Powell is a clever man who played a critical role in achieving the 2007 agreement. On the day the new ministers were sworn in, with Paisley as first minister and his deputy McGuinness taking an oath of loyalty to the Northern Ireland police service, Powell writes: “I felt dizzy and slightly faint, as if I had just finished pushing a very large boulder uphill.” He does not remark on the irony that the fanatics, reformed or otherwise, now crow atop the Ulster dunghill, while the political corpses of decent men, Protestant and Catholic alike, lie mouldering among the weeds. Maybe this is how such stories always come out, but it is not a pretty sight.

Students of government will find Powell's book a treasure trove. It provides a window upon the self- image of the Blair government, rather as The West Wing reveals the Clinton White House as it liked to imagine itself. The rest of us are entitled to deride the piety of Powell's narrative, while applauding the merciful outbreak of peace.

GREAT HATRED, LITTLE ROOM: Making Peace in Northern Ireland by Jonathan Powell
Bodley Head £20 pp352

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