Whenever discussion turns to the causes of the Irish “Troubles,” the decades-long terrorist campaign of the Irish Republican Army to force the British government to relinquish Ulster as part of the United Kingdom, it inevitably focuses on the terrible events of January 30, 1972, known to both sides of the conflict as “Bloody Sunday.” For that was the day on which a political demonstration in what used to be called Londonderry (but is now called “Derry,” its de-anglicized name, by most Roman Catholics) turned into a massacre. British paratroopers fired upon the crowd, killing 13 people and wounding another 15, and what had until then been a campaign of mass civil disobedience turned into a full-scale terrorist war which was to cost the lives of over 3,500 people during the next quarter-century.

What precisely happened during those tense, dramatic, lethal hours was the subject of speculation, assertion, counterassertion, and, above all, of Irish Republican myth-making for 26 years until, in 1998, as part of the British government’s peace deal with the IRA, a full-scale government inquiry was instituted under Lord Justice Saville. Astonishingly, the inquiry then took half as long to investigate Bloody Sunday and report upon it as the entire Troubles themselves had taken. 

The statistics are still staggering. The Saville Inquiry took a full 12 years, heard the testimonies of thousands of people, filling 10 huge volumes, and cost the British taxpayer no less than $305 million in lawyers’ fees and other expenses. All that, over something that happened 40 years ago, in which 108 rounds were fired in a few minutes. And the equally extraordinary thing is that, despite it all, we still cannot be certain about precisely what happened that day. (Nor was it even the first inquiry into the events of that calamitous day: Lord Chief Justice Widgery had already undertaken one back in the 1970s.)

Douglas Murray, an award-winning British political journalist and associate director of the Henry Jackson Society, attended hundreds of sittings of the inquiry and has read all 10 volumes of the Saville Report, and much else besides. As well as, of course, wanting to understand what really happened that day, he was interested in the wider question of, as he puts it, “how any truth can be uncovered after such a long time—what people remember and what they forget. And what happens when things turn up from the past that might have been easier left undiscovered.”

One thing that the Saville Inquiry made very clear was that, by the 1990s, British intelligence had thoroughly infiltrated even the highest levels of the IRA. Stakeknife was the code name given to Freddie Scappaticci, who rose to be deputy head of the IRA’s “nutting” (i.e., execution) squad, yet also turned out to be a longtime informant for the British domestic intelligence service, MI5. IRA chief Gerry Adams had a driver who worked for MI5, and one of Adams’s closest aides, Denis Donaldson, was also an informant. All of these men were immensely brave, as was Sean O’Callaghan, a member of the IRA’s ruling council who also worked for the Irish police force, the Garda. When the IRA discovered members who were working for MI5, they were tortured before being killed. 

Another high-ranking British agent is still today only known by his code name: Infliction. One of the top-secret documents submitted to the Saville Inquiry showed that, at a debriefing in The Hague in 1984, Infliction told his MI5 handler (known only as Officer A) that “Martin McGuinness had admitted to Infliction that he had personally fired the shot from the Rossville flats in Bogside that had precipitated the Bloody Sunday episode.” The next 19 lines of type on the page were redacted. If ever there were a (almost literal, in this case) “smoking gun” in the whole grim story of that day, it is surely this. Yet McGuinness, who naturally denies everything, went on to become a minister under the crown, and last month was photographed shaking hands cordially with the queen. 

If Martin McGuinness did, indeed, fire on the paratroops first, deliberately escalating the demonstration into what the IRA had always wanted—a shooting war—then he must bear a good deal of responsibility for the tragedy that ensued. The simple black-and-white explanation that the British Army provoked the Republicans and were entirely to blame for Bloody Sunday is clearly not good enough, although that was the substance of what Saville finally reported in 2010, and for which David Cameron apologized in the House of Commons. 

“What turned up before Saville was often as much about the present and future as it was about the past,” concludes Murray in this brave, revelatory, and gripping book, “an effort at truth and reconciliation that woke some ghosts just as others were being laid to rest.”

Andrew Roberts is the author, most recently, of The Storm of War: A New History of the Second World War.