So it was all the more shocking when the 21-year-old hanged himself in July 2003. His body, Mr McGregor says, was covered in cuts. His testicles were black and blue with bruising.
It is a case that echoes those at the notorious Deepcut barracks in Surrey: a bereaved parent denied so much information they can't help believing there's a sinister reason for covering up their child's death.
The latest of the Deepcut investigations, the results of which were released on Friday, also carries an air of secrecy - the full report may never be made public.
What exactly happened to Lance Corporal McGregor is still unclear. The incomplete information Mr McGregor has is that his son went absent without leave in order to escape bullying after being transferred to Ballymena in Northern Ireland. "I've been told nothing," he said yesterday. "I can't get access to information. The Army tell us nothing."
After Deepcut, where four young recruits were found dead in mysterious circumstances, this was supposed to have changed. A number of inquiries - none of which has satisfied the families - criticised the lack of transparency in dealing with parents.
The conclusions of the investigation by Devon and Cornwall police into the handling of the cases by Surrey police, released on Friday, runs to 150 pages. Only a six-page summary has been released, in order to protect the identities of those who gave "candid and frank" interviews in the belief they were doing so anonymously, Surrey police say. The six-page summary says the investigator became aware of documents obtained by the father of Private Gray, Geoff. One of these revealed that Surrey police had wanted to shift public opinion away from the perception that the recruits had been murdered.
"The issues raised went to the heart of the [terms of reference]," the summary says. "The senior investigating officer voiced his concerns the review could not be concluded without reviewing this new issue. Surrey police subsequently decided no work should be undertaken into these new documents. As a result the findings of this report do not take into account these unresolved issues."
When Lance Corporal McGregor was caught he was kept in a room and made to sit on a metal box - allowed off only for meals and toilet breaks, his father claims. Somewhere along the way he picked up a severe beating. He was transferred to Catterick in North Yorkshire and then became the 13th soldier to die at the camp since 1996.
More than two years on there has still been no inquest. The details of two police investigations and the Army's own inquiry have not been given to Mr McGregor. He had to request medical records under the Freedom of Information Act.
"The Army has been told by the coroner to give us their board of inquiry report but they haven't," he says. "The police have carried out two investigations and told us nothing. I've rung up Derek's friends in the Army and they've been told not to talk. All I know is that I saw him lying there at Catterick and he had cuts to his face and stomach, bruising and a black eye. I don't know what to believe because I've been lied to. If the Army didn't put that rope around his neck, then they forced him into a corner where he saw it as his only way out. It tears me apart, and it's worse because they won't tell us anything."
It is more than 10 years since Private Sean Benton was found dead with five bullet wounds to his chest at the Surrey barracks in June 1995. That November Cheryl James, 18, was found with a single bullet wound to the head. In September 2001 Private Geoff Gray, 17, was discovered with two gunshot wounds in his head. And in March 2002 James Collinson was found with a single gunshot wound to the head. A decade on, the exasperated families believe they will learn the truth only from a public inquiry.
What is known about the culture of bullying at Deepcut has come from unofficial sources. The Independent on Sunday spoke to a former Deepcut recruit who trained at the same time as Cheryl James. He said she was "degraded" to such an extent that she felt worthless. He also described a culture of violence and intimidation orchestrated by "psychopathic" instructors who were sent to the barracks in order to keep them away from serving units.
These claims are lent credence by a defence select committee report published earlier this year. It said the decision to send Leslie Skinner, a physical training instructor who had been convicted of indecent assault of young soldiers, to Deepcut where he committed further offences showed a "disturbing level of indifference or incompetence".
The soldier said: "Cheryl was a happy girl. Her confidence was growing all the time. Then she went downhill. She was ordered to an NCO's room to do his kit for him. Cheryl thought he was going to try it on, but she had to obey the order. It was an attempted rape, but she managed to get away.
"After that he had it in for her. He used to tell everyone 'I'll make her life hell'. Cheryl was a lovely lassie, but after that the spark went out of her. Three or four weeks later she was dead. She was made to feel like a piece of shit." The soldier, who wishes to remain anonymous, continued: "There were 150 recruits, with four or five in charge. They could do whatever they liked. Cheryl was publicly humiliated on parade, thrown to the ground. They would get her on her own and make sexual innuendoes to the point that she started to believe she was horrible.
"There was one guy who would throw people out of a second-storey window. He was a psychopath. They would take people out on parade naked and defecate on them. They'd tip recruits out of bed at 3am in early November, throw them down flights of stairs and strip them naked. Then they'd stand them up against a wall and throw darts at them, and say you can't go back to bed until a dart sticks in your stomach."
Surrey police say they "make no apology" for the "lack of focus" which is criticised in the Devon and Cornwall report, which took two years to compile, arguing that a wider focus has led to positive changes in the Army. The force adds that it asked that the newly discovered documents be ignored because they were concerned over the length of time the review was taking, and point out that the Independent Police Complaints Commission has its own investigation and received a copy of the documents discovered by Mr Gray.
Only five people will see the full report and the families again say they are being denied the truth. "We should see the full report," Geoff Gray said. "It directly concerns the death of my son. I want that report."
Joan Humble, the Labour MP for Blackpool North, who also co-ordinates the Deepcut and Beyond Campaign of nearly 50 families whose children have died non-natural deaths at army camps, said: "There are too many families who are finding it extremely difficult to get answers from the MoD. Families have to constantly battle to get information. They deserve to be treated better."
The Ministry of Defence said it could not comment on Mr McGregor's case while the inquiry was still ongoing.Reuse content