It was a tragedy, but a straightforward one, at least that is what the police believed. A young RAF firefighter, 24-year-old Robert Fleeting from East Kilbride, was found dead in his room on a base in Oxfordshire, having fashioned a noose from a curtain and hung himself from the door closing mechanism. Just to wrap up the instant conclusion there were suicide notes, albeit scrawled and chaotic, addressed to his family and scattered around the room.

The circumstances surrounding the death also seemed clear. On the night before, Saturday September 3 2011, Robert and some of his colleagues from RAF Benson went out for the night in nearby Henley, where they were joined by medics from the base. There was drink taken but according to those that were there Robert danced, appeared to be happy and was not drunk.

Next day, Sunday, Robert was not due to go on shift until the later afternoon but when he did not turn up for an early lunch two of his friends went looking for him. They knocked on his door but got no reply. The room was on the ground floor, they then went round to his window and found the curtains half drawn. Through the window, according to their statements to the police, they could see a made-up bed and concluded that it had not been slept in.

The two then drove around to look for Robert and then, joined by a third friend, they tried the shower room and the toilets before returning to the bedroom, trying to open the door which gave only two inches, indicating that it was blocked. One of them then recalled a small window of the room being open so the three returned to the other side of the building, one of them climbed on another's knee, pulling back the curtain, which is then that Robert's body was seen hanging behind the door.

Here the procedures, the investigation, become, at best, extremely sloppy. A doctor serving with the air ambulance is instructed to attend with two paramedics. He later testifies that he could tell just by looking through the window that Robert was dead. An RAF corporal arrives on the scene, he and a paramedic clamber through the window leaving muddy footprints on the sill, but rather than immediately cutting down Robert they collect notes from the floor and put them on top of their muddy prints.

Shortly after officers from Thames Valley police arrived at the scene and began to take statements. A torn green t-shirt is found in the room, along with broken scissors, and the later speculation is that Robert may have tried to cut up the shirt to form a ligature before resorting to the curtain, and that heavy boots of those coming through the window shattered the scissors.

Throughout their search, starting at approximately 11.30am, Robert's colleagues had been phoning his mobile phone, which on each occasion was unanswered. Around three hours later the missing phone was returned by a medic we will call Ray (still serving in the RAF), who had been on the previous evening’s jaunt to Henley. Belatedly he handed it over to the investigators.

In his statement to police Ray claimed that he had quarrelled with Robert the previous night, had called him a 'dickhhead', but they had made up on return to the base, he'd then invited Robert back to him room for a drink. There was no independent corroboration of this meeting and no forensic examination of the room.

Over a couple of beers Robert had allegedly told Ray he was having trouble with his Dad, Charlie, but he did not seemed stressed, rather chilled-out. Around 3.30am, according to the statement, Robert left, saying he had to work next day. It had all been, according to Ray, totally uneventful.

However, forty-three days later Ray dramatically changed his statement giving a radically different version of events, based on information he had been given about Robert’s post-mortem, information that his parents had not yet been given.

'Rob had not had as much as me and was slightly less drunk,' he now stated 'and still in control and like me was aware of what was going on around him.'

He had invited Robert back to his room for a drink, he said, and now, although he could not properly remember the conversation, it may have been about family, and they ended up kissing, on Robert’s initiative, and then having sex.

This changed statement was given after Ray was made aware that the post-mortem had discovered that Robert had suffered rectal haemorrhaging and bruising shortly before death.

According to this new account, “Rob asked me if I had any condoms and I got one for him. He put this on himself and had sex with me. I think there may have been some oral contact but I'm not sure. I did not have sex with Rob, it was just him having sex with me. I am aware that Rob had some rectal bruising but I have no idea how this occurred as I did not touch him in this area at all. It could be he had sex with someone else before me or did something to himself.'

Thames Valley police, whose investigation was later slated by the independent police complaints body, not only did not examine Ray’s room, they did not take fingerprints or a DNA sample from him, despite there being three samples on the noose and three on the green t-shirt, which was not Robert’s size.

His underwear and socks were also missing and have never been recovered.

Robert’s family claim they asked the investigating officer to have these checks carried out, and were refused, because Ray “has done nothing wrong”.

The post-mortem took place at the John Radcliffe hospital in Oxford two days after Robert’s death, which is when the rectal damage was detected. Any chance of a second post-mortem vanished when the body was returned to the family - still unaware of the findings - and cremated, with permission of the police, less than two weeks after the death. The funeral was on September 15, Battle of Britain Day.

Robert's parents, Charlie and Susan are the kind who don't give up on a kid, even beyond the grave. They have not believed from first being told of his death that their son killed himself. Charlie says that he has no problem, if true, that Robert had a homosexual encounter but until then he was entirely heterosexual. He had had several girlfriends, he was engaged to be married and had just given his fiancee £300 for a wedding dress.

When they did eventually see a post-mortem report there seemed to be more confusion. The initial account says that there were two puncture abrasions and other signs of external injury, a second version corrects this to say there were 'no other' signs, claiming the correction was because of a typing error.

Both versions confirm there were no drugs in the body, the stomach contained a 'small amount of semi-digested food residue and smelt slightly of alcohol'. Robert’s rectum showed a haemorrhage 'in keeping with a traumatic aetiology...suggesting recent anal intercourse'.

“Two police officers came to the door and told me that Robert had passed away,” Charlie recalled, “and gave me a number to call, It was RAF Benson. I was told immediately that Robert had hanged himself in his room. The police officer in charge, also said later it was ‘a classic suicide’. But the more inquiries we made the more inconsistencies emerged.”

At the inquest in April 2012 the Oxfordshire coroner Nicholas Gardiner concluded that Robert had taken his own life. “One difficulty which has been put to me is the fact there is no indication he had homosexual tendencies prior to this event,” he said.

“That is one powerful argument - that he might have been distressed that a homosexual act had occurred. That would have been a dreadful blow to someone who was engaged to be married. I strongly suspect it was that realisation which caused him to take the action he did. If he did take that action, I cannot conceive it would be an accidental event given the notes that he left.”

The ‘suicide’ notes, addressed to family members, scrawled and sprawling, apparently written when intoxicated, were likely to be Robert’s, according to an expert handwriting witness.

“We don’t believe these to be Robert’s,” Charlie told the Sunday Herald. “His grammar and girlfriend’s name are wrong. Robert was very close to his sister and if he was leaving this world he would have mentioned Stacy-Anne.”

The family’s claim that it had been a slipshod investigation was confirmed after they complained to the police watchdog, the Independent Police Complaints Commission, whose subsequent report revealed a catalogue of failings by Thames Valley Police. Crucially it found that the investigation had failed to explain how Robert had suffered the internal injuries before he died.

It also criticised police for failing to adequately explain how the young RAF firefighter had hanged himself from a door closing mechanism which was almost a foot above him. And which fell apart in a reconstruction.

"For Robert to have suspended himself from the door closer, consideration should have been given as to whether he could have done this himself, but there was no reference to any investigation on the point," said the report.

The report also questioned the failure of the inquiry to establish whether a specialist knot, which was used to create the ligature out of the curtain, was one that the RAF man could perform. Charlie Fleeting claims that he could not.

And, perhaps most importantly, the IPCC also slated the police for accepting the word of the key witness, Ray, despite him giving contradictory statements.

“Right from the start police made up their minds that it was a suicide, there was no proper investigation,” Charlie maintains. “No investigation of the (Ray’s) room, no fingerprinting, or DNA, no explanation of the t-shirt which clearly wasn’t Robert’s, no explanation of where his underwear went to.”

The family have now obtained a penal notice from court ordering police to hand over all of the files on the case. Thames Valley have until November 2 to do so. The force did not respond to a request for comment.

The RAF conducted their own inquiry into the death but it has not been shared with the parents or made public.

“This was their Deepcut,” said Charlie, comparing it to the series of deaths and malevolent culture at the Army base in Surrey.

Social media postings from personnel at RAF Benson appear to confirm this, with sexualised photographs, apparent debauchery, and others showing figures hooded and tied up with ropes.

Charlie and Susan Fleeting believe that their son was ‘beasted’ in a prank that went too far, that he was raped and murdered in his room. Whether or not that is the case they will clearly not stop trying to prove it.

“I want to be able to tell Robert to rest in peace,” Charlie said, “and I can’t do that until those responsible for his death are brought into court and convicted.”