He remembers the older boy's kindness in the orphanage. There was a blizzard and the snow lay too deep for him to walk to school. "So Paddy Joe hoisted me up and carried me on his shoulders," says Gerry McCann.

"I was five years old and he was 10. He was so thoughtful and giving. He made a big impression on me." Just over a decade later, Paddy Joe Crawford was dead. He was found hanging from a rope in June 1973 in Long Kesh, where he'd been interned, apparently having committed suicide.

But McCann never believed it was suicide: "I was only 16 when Paddy Joe died but even then I was suspicious that his IRA comrades had killed him. Prison would hold no fear for a boy who had grown up in institutions. He was a soft target for the IRA because he had no family to ask questions and make a fuss after his death.

"I was only out of the home a year myself, living in digs and trying to find my feet in Belfast. I knew how ruthless the IRA was and I wasn't brave enough to do anything about it then."

But it preyed on McCann's mind for decades. Two years ago, he began his personal quest for the truth about Crawford's death. Under the Freedom of Information Act, he has secured prison files which point to an IRA cover-up.

He has met Gerry Adams, leading IRA man Bobby Storey, and an IRA Army Council member in his search for answers. He has also spoken to ex-IRA prisoners in jail at the time of Crawford's death. They have told him Crawford was murdered.

And, amazingly, he has discovered that his friend was not an orphan at all but came from a republican family. Paddy Joe Crawford was 11 days old when he was placed in the Nazareth Lodge orphanage in Belfast. When he was 15, he was moved to digs on the Falls Road.

"It was tough for the orphans," says Fr Matt Wallace, a Co Wexford-born priest who ran a youth club where the boys met when they left care. "They found it difficult to get jobs. Employers would take advantage. It was lonely for them too. Lads like Paddy Joe, raw out of an orphanage, were vulnerable and easily influenced."

Crawford worked as a labourer and tried hard to fit into his new community. He was often seen on the streets: playing football with the local kids or holding a skipping rope for the girls. Friends said he was deeply affected by the 1969 pogroms when loyalists burned hundreds of Catholics from their Falls Road homes. He joined the IRA.

Breaking in Castlereagh

Seamus, then a member of the Fianna (the IRA's junior wing) says: "Paddy Joe saw the IRA as defending the people. He often used our house as a safe house. I remember him opening up on the Brits with a Thompson sub-machine gun, then sprinting half a mile back through the streets. He gave his heart and soul to the republican movement."

In April 1973, Crawford and 11 others were arrested in Newry returning from an IRA training camp. Among those detained was the late Pat McGeown who went on to join the 1981 hunger strike and become a senior Sinn Féin representative.

In Castlereagh, detectives routinely tortured suspects. Crawford, like hundreds before and after him, broke and passed on information. He admitted this to IRA intelligence officers debriefing him in Long Kesh. They reported back to the Belfast Brigade Officer Commanding (OC), Gerry Adams.

Breaking in Castlereagh never carried a death penalty but, for whatever reason, Crawford was treated differently. On Sunday 3 June – 64 days after entering Long Kesh – he joined his comrades at mass. Then, the prisoners held a parade.

A key group of inmates didn't attend. They were setting up Crawford's murder in the woodwork hut. But they were disturbed. A republican who was in Long Kesh at the time says: "Other prisoners accidentally walked into the hut. They saw Harry Burns, Thomas 'Tucker' Kane, and Jim McCormick with Paddy Joe Crawford.

"They saw a rope, a chair and a black cloth. They thought the men were only putting the frighteners on Paddy Joe. They'd no idea he was about to be killed so they left."

Later, other prisoners discovered Crawford hanging from the rope – made from a prison mattress.

Ex-internee Bobby Devlin describes the horrendous scene in his book Seagulls: "There was Paddy Joe Crawford hanging ... his neck stretched grotesquely like a turkey hanging in a butcher's shop window. He veered slowly like a discarded Christmas decoration."

The prisoners cut Crawford down with a Stanley knife. Devlin and the Cage Five OC, Paddy Joe Rice, tried frantically to save his life giving him mouth-to-mouth and cardiac massage. "There were tears in our eyes as we shouted 'Paddy, Paddy' but he appeared to be in a deep sleep," Devlin recalls.

Prison medical staff pronounced Crawford dead. His body was placed on a stretcher and covered with a sheet. The prisoners lined up on either side as it was carried out. Crawford's left hand slipped out from under the sheet. Rice took it in his own and held it. The prisoners then gathered in the canteen for a decade of the rosary.

The republican source says: "Over coming days, word slowly spread among the prisoners that Paddy Joe hadn't committed suicide. I kept waiting for it all to come out. I thought the autopsy would show he'd been killed and the police would take action but nothing happened.

"Whenever a prisoner raised the killing with the leadership outside, he was ordered to drop it. The IRA had stooped low. Paddy Joe wasn't a tout, he just broke in Castlereagh. Nothing happened plenty of men who were touts and took a weekly wage from the Special Branch. They're still walking around today."

Claims of suicide

After the murder, the cover-up began. To carry more weight, Harry Burns claimed to be the Cage Five OC when in fact he was the adjutant and Paddy Joe Rice was the OC. Unknown to the other prisoners, Burns alone made representation on their behalf about the death. He refused to give evidence to the inquest, but made a written statement falsely claiming Crawford had been acting strangely and talking about death.

He produced what he said was a suicide note. It was just a prayer that the orphans had learned in the home with a signature – in apparently different hand-writing. Fr Wallace says: "It was all very peculiar. I was at the inquest which was held very quickly – just 12 days afterwards. In other cases of controversial deaths, families have waited 12 years for inquests."

The inquest found Crawford had committed suicide. Wallace says: "I was unconvinced but I was too green to do anything. I was a priest in my 20s, just up from Wexford, who knew nothing of the IRA." The funeral was bizarre. As an IRA member, Crawford should have been buried with military honours. Yet there was no tricolour, beret or gloves on his coffin and few republicans attended.

Twist of fate

Crawford's murder remained shrouded in secrecy until four months ago when Ed Moloney's book Voices from the Grave, which includes Brendan Hughes' memoirs, was published. Hughes accused Gerry Adams of ordering the murder. The book also referred to Gerry McCann's previously unknown quest for the truth.

"I then received a phone call at the golf club I manage," McCann says. "It was made on behalf of the Pettigrews, a West Belfast family, who said Paddy Joe was related to them. That night, I met his half-brothers and sisters and learned the heart-breaking story behind Paddy Joe being placed in Nazareth Lodge."

Catherine Crawford, a single woman from a staunch Catholic family, had become pregnant to a Protestant. She wanted to keep the child but her mother said that would shame the family. The baby was given to the nuns against Catherine's wishes. She visited him many times in the orphanage. Later, she married a man named Pettigrew with whom she would have 10 children.

She made plans to take Paddy Joe home. But her mother still disapproved and the church wouldn't have allowed it anyway. When her son left the orphanage aged 15, Catherine heard he was in digs in Beechmount, off the Falls. She started shopping there. Her family couldn't understand why.

In June 1973, they discovered the reason. "Catherine phoned her older sons and daughters. She asked them to meet her in Milltown cemetery," says McCann. "When they arrived, she explained that her son, and their half-brother, was being buried."

Three months after Catherine's phone call, her eldest daughter Anne-Marie Pettigrew (19) was killed when the bomb she was handling detonated prematurely. McCann later learned that Paddy Joe Crawford knew his half-sister as an IRA comrade. But while Crawford was shunned in death by the IRA, Pettigrew was buried with full republican trappings. Her name appears on the IRA's roll of honour. A wall mural was painted of her.

Catherine died several years ago. "Paddy Joe's half-brothers and sisters are lovely people. It's very hard for them," says Gerry McCann. "They're Sinn Féin supporters and Gerry Adams is a family friend."

McCann has held three meetings with Adams and one with leading IRA man Bobby Storey: "At the first meeting, Adams denied Paddy Joe was an IRA volunteer. He said he'd killed himself in Long Kesh. Five months later, I met Storey. He admitted Paddy Joe was a volunteer but insisted he'd committed suicide.

"At two meetings since then Adams has changed his position and acknowledged Paddy Joe was in the IRA but he's still saying there is no evidence the IRA killed him." McCann wants Crawford to be publicly recognised as an IRA member with his name placed on the roll of honour. He also wants the republican movement to admit it killed him and to say sorry.

Sinn Féin set up two meetings for McCann with an IRA Army Council member. The last took place a fortnight ago. "The IRA is suggesting that Paddy Joe's name may be placed on the roll of remembrance. That's a positive move but I still want an apology for the murder and recognition that an injustice took place," he says.

The three men named to the Sunday Tribune as Crawford's killers are themselves dead. Harry Burns and Jim McCormick died of natural causes. Tucker Kane was killed in a road accident.

Paddy Joe Crawford is buried with fellow orphans Pat Devaney and Gabriel Savage, who were murdered by loyalists. Gerry McCann and Fr Wallace tend his grave. "Paddy Joe was like a brother to me," McCann says. "He is my family and I want the truth to be told."