The official version, the conspiracy theories and the evidence surrounding David Kelly's death.
Was Dr Kelly's body moved?
Dr David Kelly's body was found at 9.20am on the 18 July 2003 by two volunteer searchers, Paul Chapman and Louise Holmes with the help of their search dog.
They said they took care not to disturb the scene or get too close to the body, and contacted the police as soon as they found Dr Kelly. Their description was of a body "slumped" or "sitting ... up against a tree".
The searchers told a police officer, DC Graham Coe, how to find the body, and he stayed alone with it for 30 minutes. DC Coe said he only observed the scene and never got close to the body and stayed about seven or eight feet away
Rowena Thursby of The Kelly Investigation Group says: "When the other people came along, the paramedics, the policemen, the detective, the forensic pathologist - all those people subsequently said that the body was flat on its back, not touching the tree at all. So completely horizontal on his back, so, which indicates to me, to anybody sensible, that the body was moved".
So while the searchers describe the body as sitting up against a tree, everyone afterwards suggests a different position.
The paramedics describe "a male on his back" and a body "laid on its back", DC Coe describes a body "laying on its back by a large tree head towards the trunk of the tree" and Dr Nicholas Hunt, the Home Office forensic pathologist describes a body "lying on his back".
Lord Hutton says that such discrepancies in eye witness accounts are quite normal and do not disturb him.
He saw a photograph of the body that he believes are consistent with all the descriptions given and he concluded there was no involvement by a third party in Dr Kelly's death: "I have seen a photograph of Dr Kelly's body in the wood which shows that most of his body was lying on the ground but that his head was slumped against the base of the tree - therefore a witness could say either that the body was lying on the ground or slumped against the tree. These differences do not cause me to doubt that no third party was involved in Dr Kelly's death."
A lack of blood?
In December 2004, 11 months after Lord Hutton's report was published, the paramedics who attended the scene of Dr Kelly's death took the unprecedented step of calling a press conference.
Dave Bartlett and Vanessa Hunt had attended dozens of suicide attempts in which someone has cut a wrist. But they said that they found the scene of David Kelly's death unusually free of bloodstains.
At this press conference, Dave Bartlett said: "I suppose everyone was surprised at the outcome. Like I say we're not medical experts, all we commented on was the amount of blood over the body."
Vanessa Hunt added: "We can only say what we saw on that morning and there just didn't appear to be a substantial amount of blood loss either onto the clothing or around the area."
The Hutton Report had different witness accounts, and some saw more blood.
The pathologist Dr Nicholas Hunt said there was a "significant volume of blood" and the forensic biologist Roy Green said that there was "a fair bit of blood" consistent with a severed artery, and some had soaked into the ground. Neither of them would speak to the programme to clarify exactly what they meant.
Lord Hutton said in his report: "Those who try cases relating to a death or injury (whether caused by crime or accident) know that entirely honest witnesses often give evidence as to what they saw at the scene which differs as to details.
"In the evidence which I heard from those who saw Dr Kelly's body in the wood there were differences as to points of detail, such as the number of police officers at the scene and whether they were all in uniform, the amount of blood at the scene."
Dr Allen Anscombe, a Home Office pathologist and the president of the British Association in Forensic Medicine told The Conspiracy Files: "The actual volume of blood, given that the person is deceased, is likely to be fatal, whatever that volume happens to be.
"There is not a simple volume which is always fatal and a simple volume which is not. It depends on the rate of bleeding, it depends on your physical condition before you're bleeding and whilst you're bleeding, depends on a number of factors".
Is it possible to die by cutting the ulnar artery?
Dr David Kelly is the only person to die by severing an ulnar artery in 2003. A group of doctors have published letters questioning whether it is possible to die by severing the ulnar artery, which is a relatively deep artery in your wrist and arm.
One of them is vascular surgeon John Scurr, a specialist in veins and arteries. He told the programme: "I don't think I've ever seen anybody die from wrist injuries. I have seen a lot of wrist injuries. It is a very common cry for help type of attempt at suicide, rather than a genuine attempt at killing themselves.
"Frankly I don't believe that simply cutting an ulnar artery will cause death. The thing we know about the ulnar artery is it's quite small and so if Dr Kelly had cut it clean it would have gone into spasm and it would have, you know, probably oozed for a little while trickled.
"He might have lost a few hundred mills of blood. And then it would have stopped."
However, according to the National Statistician and Registrar General there are other recorded cases of death being caused by a severed ulnar artery, two in 2001, one in 2002, and one in 2004.
Dr Allen Anscombe, the president of the British Association in Forensic Medicine is a Home Office forensic pathologist who has performed thousands of post mortems.
He told the programme: "Forensic pathologists are biased in terms of seeing what people actually die from. Clinicians by and large, the vast majority of their patients don't die.
"So again, we approach things from a different way and actually see what people really die from. You might argue we don't see what people survive. So I'm quite happy to accept that often severed small to medium sized arteries such as ulnar artery are not fatal, but severings of such an artery can and is occasionally fatal.
"And if you combine that with somebody who is deceased then you tend to put two and two together".
Was there a fatal overdose of co-proxamol?
Officially, David Kelly's death was not only caused by haemorrhaging from a wrist wound. Lord Hutton says that an overdose of the painkiller co-proxamol probably also played a part:
"It is probable that the ingestion of an excess amount of co-proxamol tablets coupled with apparently clinically silent coronary artery disease would have played a part in bringing about death more certainly and more rapidly than it would have otherwise been the case."
Packaging found with his body meant that up to 29 co-proxamol tablets were available to Dr Kelly.
But the toxicologist who gave evidence to the Hutton Inquiry could not be definitive about how many tablets were taken.
Tests the toxicologist carried out suggested it was an overdose, and that Dr Kelly had 10 times more than a typical medical dose of co-proxamol. But he also said that the concentrations of the constituents of co-proxamol found in Dr Kelly were less than is usually fatal.
The Medicines and Healthcare Products Regulatory Agency say that "Co-proxamol was implicated in between 300 to 400 deaths from overdose a year," which is why it is now being withdrawn from the market.
The Conspiracy Files interviewed Professor Robert Forrest, Britain's foremost forensic toxicologist who is also the President of the Forensic Science Society. He said: "The concentrations in Dr Kelly's blood are on the low side.
"We normally see higher concentrations than that in a person who has died of an overdose of co-proxamol. But if you've got heart disease - and if there is something else going on like blood loss, then all three of those are going to act together. The overdose of co-proxamol, the heart disease and the blood loss."
And Professor Forrest concluded: "I've got no doubt that the cause of Dr Kelly's death was a combination of blood loss, heart disease and overdose of co-proxamol.
"Not necessarily in that order. If I was going to put it in order I'd put the overdose of co-proxamol first. But it's important that all of them had interacted to lead to the death".
Did the Hutton Inquiry prove that Dr Kelly intended to commit suicide?
Lord Hutton concluded that the major factor behind Dr Kelly becoming suicidal was "a severe loss of self esteem resulting from his feeling that people had lost trust in him and from his dismay at being exposed to the media."
As the source for Andrew Gilligan's report, which formed the basis of an unrelenting and bitter dispute between the Government and the BBC, Dr Kelly undoubtedly went through a very stressful period.
For several weeks he was under suspicion and interviewed by the MoD twice. Finally Dr Kelly was named publicly and he was questioned in a televised session of a parliamentary committee.
However, Dr Kelly spent many years doing a very difficult job in a hostile environment, making 37 visits as a UN Weapons Inspector to Iraq.
Would he have buckled and killed himself during a period of stress?
Not according to one of his UN Weapons Inspection Team colleagues, Richard Spertzel: "One of the reasons I didn't accept the suicide story from the beginning is I would not consider David a person that would become suicidal.
We all have depressions. There are some of us, and David is included in those, that would endure and find other ways out."
On the last day of his life, Dr Kelly was telling friends that he would continue with the job that was so important to him. He was replying to messages from friends and colleagues that he would soon be back in Baghdad. His daughter was due to get married in three months.
"I would feel it most unlikely that he would want to essentially abandon his family and end his life prematurely," said Mr Spertzel. "He certainly could have looked forward to many more years of happy life."
Amongst the e-mails on that last day, there was one message which does not appear to show that Dr Kelly was a threat to himself, but that he felt threatened by others. He told his friend, journalist Judith Miller that there were "many dark actors playing games".
The key to whether David Kelly was really suicidal was his state of mind. The Hutton Inquiry heard that David Kelly told a colleague he felt "thrown" when the Foreign Affairs Committee asked him on the 15 July, 2003 about a conversation he had had with another BBC reporter, Susan Watts.
David Kelly had told the MoD that he had met Susan Watts but said he had not spoken to her about the 45 minute claim.
He was told that if new evidence came to light which called into question his account, he might face disciplinary action.
The Foreign Affairs Committee twice read out to Dr Kelly a transcript of what a source had told Susan Watts. Dr Kelly said "it doesn't sound like a quote from me" and went on to deny he was the source.
However, Dr Kelly was the source for Susan Watts' report and must have realised when a transcript of his conversation was read out it would be possible to prove he was the source and he would be considered as dishonest.
Peter Tyrer, Professor of Psychiatry at Imperial College London told The Conspiracy Files: "He was a man who was a stickler for accuracy and he was also very concerned about being honest. And I think he was concerned that this extra information which was tape recorded presumably without his knowledge might have implied that he was a liar."
When Dr Kelly's friend Professor Alistair Hay saw him face tough questioning alone in front of the Foreign Affairs Committee, he was very concerned.
"This was a very different David that I was seeing and so that made me worried really," he said.
"You just have to imagine how you would feel under those circumstances where everything that you had done your whole career which you are immensely proud of, and absolutely justifiably because it was an enormously brilliant record that he had, to think that this might all be in peril."
On 17 July, 2003, his last morning alive, Dr Kelly sent e-mails to friends saying he would soon be back in Baghdad.
Professor Tyrer has studied Dr Kelly's e-mails, and told The Conspiracy Files: "It looked as though the ones on the morning of the 17th were rather stereotyped whereas the earlier e-mails that he sent in July were much more informative and more sort of warmth coming through them.
"And I think that there was a certain detachment of those emails on the morning of the 17th of July which made me think that he'd already decided that he was going to take his own life when he was writing those."
As well as sending e-mails David Kelly was receiving them. One was about an MP who had asked a parliamentary question about what disciplinary action the MoD was going to take against him .
He took a knife he had had since childhood from his desk drawer on his last walk towards Harrowdown Hill.
"He was a person who liked to be in control and it was clear from the last few days of his life that he felt he was losing control," said Professor Tyrer.
"The uncertainty for someone who is highly meticulous, the uncertainty of what might happen, it's almost worse than the certainty of something terrible happening.
"He didn't actually know how it was going to pan out and I think that must have been extremely alarming for him. So I think it's that combination that really led to the suicide."
"He had a broken heart. He had shrunk into himself," Mrs Kelly told the Hutton Inquiry. She has not spoken to The Conspiracy Files but she told Rowena Thursby of The Kelly Investigation Group she has no doubts that her husband took his own life.
"I spoke to Mrs Kelly on the phone. And she felt that her husband had in fact, committed suicide. That was her strong belief. But you know, people can believe things very strongly but it doesn't mean to say that they're actually true."
Could Dr David Kelly have been murdered?
A number of people claim Dr Kelly could not have committed suicide and instead he was murdered. The Conspiracy Files heard several new claims that Dr Kelly was assassinated.
Richard Spertzel was the USA's most senior biological weapons inspector. He worked alongside Dr Kelly in the weapons inspections organisation Unscom for many years in Iraq and believes the Iraqi regime may have pursued a vendetta against Dr Kelly.
"David Kelly did not commit suicide. He was assassinated ... I believed that David was probably a victim of Iraqi Intelligence Service because of long standing enmity of Iraq towards David."
Warren Reed was an officer in the Australian Secret Intelligence Service for 10 years and thinks that "a key priority of some people in the political machine would have been to shut David Kelly up once and for all."
Sir John Scarlett, the chairman of the Joint Intelligence Committee, the Government's main intelligence advisor, did suggest that David Kelly needed a "proper security style interview". However, at the Hutton Inquiry Sir John said that he meant that the interview would need to be "thorough and forensic".
Warren Reed, who was trained by MI6, argues that Dr Kelly would have felt threatened by such an interview.
"They would have known how to ask questions that would have perhaps needled Kelly in a certain sort of way. They were looking for pressure points that would intimidate him.
"If indeed something like this did occur I would imagine that a top British interrogator, maybe from MI6 MI5, would have been brought in under cover. Perhaps something they picked out to do with say his personal life could have been sufficiently intimidatory to have brought on either the suicide or say a heart attack."
Norman Baker MP believes that Dr David Kelly did not kill himself, and has launched his own high profile investigation. "A small number of people have come forward with something to tell," he said.
"People who've either known David Kelly or been connected with the Government in some way, an even smaller number of people who are in the inside connected with the security services or others who may know something of what happened."
He described what one of these contacts had said to him: "He had been told by - a, a friend who was senior in the security services that this was a quote - wet disposal and what is wet disposal I asked him, wet disposal means that it was a hurried job and he was killed in a hurried way, that's apparently what wet disposal means."
However, such allegations are strongly refuted by John Morrison, who as the deputy chief of Defence Intelligence, 1995-1999, and the investigator for the Intelligence and Security Committee (1999-2004) has worked with both MI5 and MI6.
He said: "Let's use a little bit of common sense here. If Iraqi intelligence had wanted to get rid of David Kelly, where would they have done it? Iraq or the UK?
"He could have had an accident at any time in Iraq. Very hard to prove it wasn't an accident. Would they really track him down?"
Mr Morrison rejects suggestions that Dr Kelly could have been the victim of British agents licensed to kill: "It is indeed complete fantasy that there are agents that are licensed to kill.
"There are intelligence agencies around the world who do engage in assassinations, there's no doubt about that. Some of them not very nice people at all.
"But we have never had a policy of assassination to my knowledge in the history of the UK intelligence agencies, and certainly not in the last few decades".
Mr Morrison says the term "wet disposal" is only used in fiction and concludes: "I can't conceive of anybody or organisation having any motive whatsoever to kill Dr Kelly.
"In a crime such as this you need, traditionally, motive, method, and opportunity. Since there's no motive, this is the rock on which all conspiracy theories founder."
Should there be an inquest?
Liberal Democrat MP Norman Baker argues that the Hutton Inquiry was not fit for purpose and there should have been an inquest as well: "The Hutton Inquiry singularly failed to pursue any points of interest. As soon as anyone starts to say anything interesting the Hutton Inquiry moved onto something else.
"The Hutton Inquiry seemed to be there to shut down matters rather than to open them up ... People who meet violent deaths always have a proper inquest. It's extraordinary that there hasn't been one on this occasion and we ought to have one. Some of the evidence would then come out properly."
The Hutton Inquiry had less legal powers than a coroner in an inquest. People did not give evidence under oath which allows people to be prosecuted for perjury, and witnesses could not be compelled to give evidence.
Lord Hutton says he decided fairly on the basis of the evidence most of which he published.
Defenders of Lord Hutton's Inquiry say it was not impeded by the absence of statutory powers, as the huge public interest in the inquiry ensured that it had the full co-operation of all the witnesses needed.
The inquiry has also been praised for the mass of detail it uncovered.
An inquest was opened just after Dr Kelly's death, but the Lord Chancellor asked Nicholas Gardiner, the Oxfordshire Coroner to adjourn it as the Hutton Inquiry would take over.
The Conspiracy Files has published for the first time a series of letters provided to Norman Baker MP by the Department of Constitutional Affairs. They reveal that at the time the coroner wrote to the Lord Chancellor of his concern at the Hutton Inquiry's lack of legal powers when compared to those of an inquest:
"as you will know, a coroner has power to compel the attendance of witnesses. There are no such powers attached to a public inquiry."
The Lord Chancellor said at the time he had checked with the Kelly family that they preferred the inquest to be adjourned, and that "duplication of proceedings can cause unnecessary distress to the bereaved".
The inquest did hold another day of hearings but was then adjourned and the Hutton Inquiry took over.
Dr Michael Powers QC, an expert in the law relating to inquests, who has sat as a coroner, told The Conspiracy Files that the law that allowed the Hutton Inquiry to replace the inquest has only been used on three other occasions, when it could prevent unnecessary repetition of inquests in cases of multiple deaths from the same cause.
"This procedure of adjourning for a public inquiry is really still with major disasters. People die multiple deaths in a train accident or boating accident of that kind.
"So far as I'm aware, this is the first and only time when it has been used to investigate the death of a single person," he said.
Three months after the Hutton Report was published, on the 14 March, 2004, the coroner Nicholas Gardiner formally considered in an open court hearing whether to reopen the inquest.
The hearing was told that David Kelly's widow Janice accepted that he had taken his own life and did not want the inquest resumed, neither did the Lord Chancellor.
The coroner also made his decision on the basis of additional written evidence from the police. However, the details of the police report have never been made public.
David Kelly: The Conspiracy Files will be broadcast on Sunday, 25 February 2007 at 2100 GMT on BBC Two.