Peter Geoghegan: Warm welcome in Derry as 'truth is set free' after 38 years

In the course of a solemn, purposeful procession, they walked by the Bogside's low-rise flats complexes and on past William Street, each carrying a black-and-white picture accompanied by four short words, "Set the truth free".

Less than an hour later, their 38-year-old call was answered. Inside the ornate Guildhall, the group, all relatives of the 27 people killed and injured in Derry on 30 January, 1972, read the first public copies of Lord Saville's report into the events of Bloody Sunday. Despite stretching to more than 5,000 pages, this report, the result of the longest-running and costliest inquiry in British legal history, leaves no room for equivocation: the British Army in Derry fired on unarmed civilians without justification or provocation.

Acknowledging Saville's report in the Commons, David Cameron's speech – the most statesmanlike of his brief tenure – was peppered with words such as "sorry", "wrong" and "unjustifiable"; sentiments conspicuous by their absence from Lord Widgery's original, rushed, whitewashed report, published weeks after the event.

Back in Derry, thousands gathered outside the Guildhall, the city's main civic building, to watch Mr Cameron's speech live on big screens specially erected for the event. Ringed by larger-than-life photographs of the 13 people shot dead by British paratroopers – and pictures of another man, John Johnson, who died of injuries sustained that day – the people of Northern Ireland's second city came expecting answers.

Applause rippled across the crowd as the Prime Minister summarised the report's main findings: soldiers from 1 Para fired the first shots; none of the dead was armed; soldiers gave no warning. But claps audibly turned to boos as Mr Cameron praised the army's role in Northern Ireland during Operation Banner: the North's history is still a fractured and divided one.

The publication of the Saville report has been welcomed by republicans, but caused consternation among loyalists: if the deaths of 14 Catholics justify a 191 million inquiry, many ask, why do the 11 Protestants killed by the Provisionals at Enniskillen on Remembrance Sunday, 1989, or the nine dead at Claudy not deserve similar treatment?

But Bloody Sunday is different. The killers were not loyalist or republican paramilitaries, but members of the British security forces. It was the state, as Saville makes clear, that carried out these killings, the largest such incident since the Peterloo massacre in Manchester of 150 years earlier.

Saville's findings are unlikely to disrupt the power-sharing government at Stormont – not least as they cleared deputy first minister Martin McGuinness, an IRA commander in Derry and one of the 922 people who gave oral testimony to the inquiry, of any wrongdoing on Bloody Sunday. But whether or not the Director of Public Prosecutions decides to press charges against any of the soldiers involved could have important implications, particularly for the North's newly devolved policing and justice department.

"Widgery's lies have been exposed. The truth has been brought home at last," Tony Doherty, whose father, Paddy, was shot dead aged 31 on Bloody Sunday, told the crowd at the Guildhall.

Saville has set the truth free – now the attention, in Northern Ireland and beyond, will turn to what the authorities decide to do with his answers.

Peter Geoghegan is the author of A Difficult Difference: Race, Religion and the new Northern Ireland.