Ten years ago on Friday Donna Marie McGillion was shopping in Omagh with her fiancé, Garry, his sister Tracey and Tracey’s daughter Breda, who was to be flower girl at their wedding the following week.

At 3.10pm they were yards from a maroon Vauxhall parked in Market Street when it exploded, killing 29 people and two unborn babies in the deadliest atrocity of the Troubles.

Breda died. Garry and Tracey were severely injured. Donna Marie, then 22, was so badly burnt that she was identified only by her engagement ring, and the last rites were read. She spent months fighting for her life.

Today Mrs McGillion is transformed. She married Garry and has two young children. The mask she wore for three years to protect her plastic surgery is gone, but she is still disfigured. “I have built a good life,” she said, but her cheerfulness hides a deep and lasting pain. At night she hears the screams of the injured and Garry shouting for her amid the mayhem. She receives counselling and finds it hard to talk of the bomb without crying.

She has one piece of shrapnel lodged in her spine, which affects her arms, and another in her knee. She cannot work, lift her children or walk far. She takes painkillers daily, and has to moisturise her scarred body twice every day. After more than 20 skin-graft operations she has refused any more. She avoids mirrors. “I have to look to the future for my family,” she said, but admitted: “I will never forget [the bomb]. It is there when I get up in the morning and go to bed at night.”

Omagh has also been outwardly transformed over the past decade. A regeneration programme has turned a quiet market town into a lively regional hub. The street where the bomb exploded has been prettified and there are smart new boutiques and bars, a new arts centre, college, shopping mall, riverside walk and farmers’ market. The army base, which served as a temporary mortuary, has closed and there is a pioneering plan to move five schools serving Protestant and Roman Catholic students on to its 170 acres.

This outward transformation, however, conceals deep anguish. Most of the bereaved and injured simply will not talk about the bomb. Others wipe away tears as they recall the slaughter of so many innocents: mothers buying school uniforms, six children under 13, four teenagers awaiting exam results, two young women engaged to be married, tourists from Ireland and Spain, a Sunday school teacher, an altar boy.

Some people will not go near the bombsite. Some are still coming forward to be treated for post-traumatic stress. Some have been crushed by their losses or consumed by their pursuit of justice. Despite the solemn promises of Britain’s political leaders and the anti-terrorist legislation that they rushed through Parliament, not one person has been convicted and security sources say that the Real IRA, the Republican splinter group responsible for the bombing, remains an active threat.

Colm Murphy, a builder from Co Louth, had his conviction for conspiracy overturned in 2005. Sean Hoey, an electrician from South Armagh, was acquitted of murder last December.

Nuala O’Loan, the police ombudsman, and the judge in the Hoey trial have roundly condemned the police, whose failure either to avert the bombing or to convict the perpetrators has fuelled any number of conspiracy theories in Omagh, most notably that the security forces connived in the attack to end the Troubles.

It certainly had that effect. Far from destroying the fragile peace process, the massacre cemented it. It inspired such universal disgust that mainstream Republicans could not possibly resume their armed struggle. That is little consolation for those whose lives have been wrecked by the bomb. The Times arrived at the home of Lawrence Rush this week to find him writing a poem to his late wife, Elizabeth, who died in the blast. Mr Rush, 67, was sitting unshaven at a table piled high with papers in a neglected house.

He had been working on the poem for three days. He lives alone, his three grown children having all abandoned Northern Ireland after the bomb. He gave up work long ago. He is lonely, his pain has not diminished and his health has suffered, he said as he chain-smoked. He returned a £7,500 government compensation cheque, calling it an insult. His preoccupation is bringing his wife’s killers to justice and he has vowed not to erect a headstone on his wife’s grave until she can truly rest in peace. Kevin Skelton, 53, whose wife, Philomena, died in the explosion, salvaged his life three years ago when he married the mother of a deprived Romanian girl whom Philomena used to bring to Omagh for holidays. Before that he had left his lorry driving job, given up refereeing football and turned to drink. “It was pure hell,” he said. At his lowest point, “I had a double-barrelled gun under my chin with my fingers on the two triggers”.

Michael Gallagher, whose younger daughter twice tried to kill herself after his son Aidan, 21, died in the blast, runs the Omagh Support and Self-Help Group, which represents several bereaved families. It is utterly incredible that the Real IRA is still operating, he said.

Some of the group’s families are pursuing an unprecedented civil action against five named suspects because they have abandoned hope of criminal convictions. The group is demanding an independent cross-border inquiry into the security services’ performance. In a town with a strong Republican presence it also had to fight to have the words “murdered by a dissident Republican terrorist car bomb” inscribed on the £400,000 memorial that will be unveiled this Friday. For that reason many of the bereaved are boycotting the ceremony.

“Justice is a big part of closure, but sadly justice has eluded us,” Mr Gallagher said. But many of the bereaved want to grieve in private, or to put the bomb behind them now that peace has returned to Northern Ireland, and hate the way his group keeps Omagh in the news. Mick Grimes, 81, a farmer from Beragh, suffered the greatest loss. His wife, Mary, his daughter, Avril, Avril’s 18-month-old daughter, Maura, and her unborn twins all perished that terrible afternoon. He had kept a stoic silence until last week when he published his memoirs, Till We Meet Again, with just one terse chapter on the bomb.

In an interview with The Times Mr Grimes displayed an astonishing lack of bitterness. He said that it was time to forget the past and set hatred aside. “You can do it the other way but you are hurting no one but yourself,” he said. At a packed book launch in Omagh library, however, not even he could hide his pain. As he read a poem from the book he choked on the final lines: “. . . great things will be unfurled / When a gentle mother’s hand / Is allowed to rule the world.”

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