In the case of Allawi's group, it was reports passed to MI6 in the spring and summer of 2002, including the false claim that Saddam had weapons of mass destruction which he could deploy at 45 minutes' notice.
For Tony Blair it was a glorious day. He was in the United States being feted by the U.S. Congress and President Bush.
Their adulation was such that he was being offered the rare honour of a Congressional Gold Medal.Naturally enough, Bush and his administration were hugely grateful for Blair's decision to join the United States in its invasion of Iraq.
That invasion was supposed to lead to the discovery and disposal of weapons of mass destruction (WMD) and make the world a safer place.
But as Blair was lapping up the grateful plaudits from the U.S. Congress on July 17, 2003, the man who had done more than almost any other individual on earth to contain the threat from WMD lay dead in the woods at Harrowdown Hill in Oxfordshire.
For Dr David Kelly, the UK's leading weapons inspector, there was to be no adulation, no medal, no standing ovation.
His life ended in the cold, lonely wood where he was found the next morning, his left wrist cut open, and three nearly-empty blister packs of painkillers in his jacket pocket.
His death was, of course, sensational front-page news. Dr Kelly, unknown to almost everybody at the beginning of that July, had in recent days barely been absent from media headlines.
Much to his chagrin he had been thrust into the harsh glare of publicity, accused of being the mole who expressed to the BBC deep concerns about the Government's "sexing up" of its dossier on weapons of mass destruction.
For Blair - accused of misusing, exaggerating or even inventing intelligence in order to justify the overthrow of Saddam Hussein - the stakes could not have been higher.
This was undoubtedly the greatest crisis of his premiership to date.
To add fuel to the flames, his director of communications, Alastair Campbell, had launched an unprecedented and vitriolic attack on the BBC, questioning its integrity and professionalism in the way it reported the story.
Suddenly finding himself under tremendous personal pressure, it seemed that Dr Kelly had buckled and decided to commit suicide.
That, at least, was the official version of events, as decided by the Hutton inquiry, set up by the Government with lightning speed within hours of Dr Kelly's body being found.
The media, the political establishment, indeed almost everybody accepted Lord Hutton's verdict. But the more I examined it, the more it became clear to me that Hutton's judgment was faulty and suspect in virtually all important respects.
I was not alone in these suspicions. Letters began to appear in the press from leading medical specialists, in which they queried the suicide verdict.
The letters were well argued, raising profound and disturbing questions that remain unanswered to this day.Increasingly concerned, I decided to give up my post on the Liberal Democrat front bench to look into Dr Kelly's death.
My investigations have since convinced me that it is nigh- on clinically impossible for Dr Kelly to have died by his own hand and that both his personality and the other circumstantial evidence strongly militate against suicide.
Given that his death was clearly not an accident, that leaves only one alternative - that he must have been murdered.This is not a conclusion I have come to lightly. I simply set out to examine the facts, to test the evidence, and to follow the trail wherever it took me.
The account I give in this series may not be correct in all respects, but I suggest that it is rather more credible than the verdict reached by Lord Hutton.I certainly believe there are enough doubts, enough questions, enough of a smell of stinking fish to justify re-opening this episode officially.
My investigations have been a journey into the unknown, and one that has taken many peculiar turns. Perhaps the most sinister came soon after starting my inquiries last year.
After writing a newspaper article outlining my early concerns, I found myself on a train speeding towards Exeter to see a man who had agreed to meet me only on condition of anonymity and after some rather circuitous arrangements.
These involved much complicated use of public telephone boxes to minimise the chance that his contact with me could be traced.
Finally, we talked over a glass of wine in a rather nondescript club.He told me that he had recently retired but had connections to both the police and the security services, a claim which I subsequently verified through careful checks.
Like me, he had many doubts about the true circumstances surrounding Dr Kelly's death and he had begun making his own surreptitious inquiries around Southmoor, the Oxfordshire village which was Dr Kelly's home.
Posing as a freelance journalist, he had attempted to contact the key policemen involved in investigating the case. In this he was unsuccessful but within an hour he received an unexpected return call.
The person on the other end of the line did not bother with formalities, but instead cut to the quick. How would my contact welcome a full tax inspection of his business, VAT, national insurance, the lot?
Life could be made very difficult, he was told. How did he fancy having no money?
Naturally, this prospect did not appeal, and there he left matters until, at a wedding, he chanced upon an old friend whom he described to me initially as a very senior civil servant, but later as a "spook" from MI6.
He told his friend of his interest in the Kelly affair and also of the threatening phone call he had received.His friend's reply was a serious one: he should be careful, particularly when using his phone or his computer. Moreover, he should let the Kelly matter drop.
But my contact did not do so. Two weeks later he met his friend again, this time in a pub, and pressed him on the matter. His friend took him outside, and as they stood in the cool air, told him Dr Kelly's death had been "a wet operation, a wet disposal".
He also warned him in very strong terms to leave the matter well alone. This time he decided to heed the warning.I asked my contact to explain what he understood by the terms his friend had used. Essentially, it seems to refer to an assassination, perhaps carried out in a hurry.
A few months later, I called my contact to check one or two points of his story. He told me that three weeks after our meeting in Exeter, his house had been broken into and his laptop - containing all his material on Kelly - had been stolen. Other valuable goods, including a camera and an LCD television, had been left untouched.
It was sobering to be given such a clear indication that Dr Kelly had been murdered, but the scientist himself appears to have been fully aware that his work made him a target for assassins.
British diplomat David Broucher told the Hutton inquiry that, some months before Dr Kelly's death, he had asked him what would happen if Iraq were invaded.
Rather chillingly, Dr Kelly replied that he "would probably be found dead in the woods".At the inquiry, this was construed as meaning that he had already had suicidal thoughts. That, of course, is patently absurd.
Nobody can seriously suggest that he was suicidal at the time the meeting took place - yet Lord Hutton seems to have made his mind up about the way in which DrKelly died before the inquiry even began.
The result is a series of gaping, unresolved anomalies.
Crucially, in his report, Hutton declared that the principal cause of death was bleeding from a selfinflicted knife wound on Dr Kelly's left wrist.
Yet Dr Nicholas Hunt, the pathologist who carried out the post-mortem examination on DrKelly, stated that he had cut only one blood vessel - the ulnar artery.
Since the arteries in the wrist are of matchstick thickness, severing just one of them does not lead to life-threatening blood loss, especially if it is cut crossways, the method apparently adopted by DrKelly, rather than along its length.
The artery simply retracts and stops bleeding.
As a scientist who would have known more about human anatomy than most, DrKelly was particularly unlikely to have targeted the ulnar artery. Buried deep in the wrist, it can only be accessed through the extremely painful process of cutting through nerves and tendons.It is not common for those who commit suicide to wish to inflict significant pain on themselves as part of the process.
In Dr Kelly's case, the unlikelihood is compounded by the suggestion that his chosen instrument-was a blunt pruning knife.This would only have increased the pain and would have failed to cut the artery cleanly, thereby hastening the clotting process.
Statistics bear out the extremely low incidence of individuals dying by cutting the ulnar artery, with only one recorded case in Britain during the entire year of Dr Kelly's death.
Given that the average human body contains ten pints of blood, and that about half of these must be lost before death ensues, we must also ask ourselves why there were clear signs at the postmortem-that Dr Kelly had retained much of his blood.
We cannot be sure exactly how much since, inexplicably, the pathologist's report does not provide an estimate of the residual volume, but what he did record was the appearance of "livor mortis" on Dr Kelly's body.
This purplish-red discolouration of the skin occurs when the heart is no longer pumping and blood begins to settle in the lower part of the body. But if Dr Kelly had bled to death, as we are led to believe, then significant livor mortis would not have occurred. Put simply, there would not have been enough blood in his body.
More significant still, while the effects of five pints of blood spurting from a body could not easily be hidden, the members of the search party who found his body did not even notice that Dr Kelly had apparently incised his wrist with a knife.
Their arrival was followed by that of paramedics who pointedly referred to the fact that there was remarkably little blood around the body.If the idea that blood loss brought about Dr Kelly's death is flawed, still less plausible is the suggestion that he chose an overdose to quicken his end.
Mai Pederson, a close friend of DrKelly's, has confirmed that he hated all types of tablets and had an aversion even to swallowing a headache pill.Yet we are told that he removed from his house three blister packs, each containing ten of the co-proxamol painkillers which his wife Janice took for her arthritis.
Each of these oval pills was about half an inch long. Since there was only one tablet left, the implication is that he had swallowed 29 of them. If this is right, we are being asked to believe that Dr Kelly indulged in a further masochistic act in an attempt to take his life.
A further objection is that police evidence states there was a halflitre bottle of Evian water by the body which had not been fully drunk.Common sense tells us that quite a lot of water would be required to swallow 29 large tablets. It is frankly unlikely, with only a small bottle of water to hand, that any would have been left undrunk.
Stranger still, tests revealed the presence of only the equivalent of a fifth of one pill in Dr Kelly's stomach.Even allowing for natural metabolising, this cannot easily be reconciled with the idea that he swallowed 29 of them.
Forensic toxicologist Alexander Allan told the Hutton inquiry that although the levels of co-proxamol in Dr Kelly's blood were higher than therapeutic levels, they were less than a third of what would normally be found in a fatal overdose.
Furthermore, it is generally accepted that concentrations of a drug in the blood can increase by as much as tenfold after death, leaving open the possibility that he consumed only a thirtieth of the dose necessary to kill him.
As for Dr Kelly's state of mind, in the eyes of those who knew him well he was the last person who might be expected to take his own life.A recent convert to the Baha'i faith which expressly forbids suicide, he was a strong character who had survived many difficult situations in the past.
Just a day before his 20th birthday in May 1964, his own mother had killed herself with an overdose. Though this had naturally affected him deeply at the time, there was nothing to suggest that it was on his mind at this point in his life.
His friend Mai Pederson recalled a conversation they once had about his mother's death. Would he ever contemplate suicide himself, she asked. 'Good God no, I couldn't ever imagine doing that," he is said to have replied. "I would never do it."
Later many people would conclude that the seeds of his suicide lay in his uncomfortable appearance before MPs on the Foreign Affairs Committee on Tuesday, July 15, just three days before his death.
Grilled for more than an hour during this televised hearing, he was clearly under considerable pressure and yet one journalist recalled him smiling afterwards.
By the time he gave evidence before the Intelligence and Security Committee the following day, he was even managing to crack a joke or two.His emotional state certainly did not appear to give any major cause for alarm on the morning of the Thursday he disappeared.
His wife Janice later described him as "tired, subdued but not depressed" and the e-mails he sent from his home during those hours suggested that his mood, if anything, was upbeat.
"Many thanks for your thoughts," he wrote to one colleague. "It has been difficult. Hopefully will all blow over by the end of the week and I can travel to Baghdad and get on with the real work."Indeed, so keen was Dr Kelly to get back to Iraq that he spoke to Wing Commander John Clark at the Ministry of Defence about when he could return.
A trip was booked for him the following Friday and his diary, recovered by the police, shows that the trip had been entered for that day. People about to kill themselves do not generally first book an airline ticket for a flight they have no intention of taking.
Since none of this fits the profile of a man about to commit suicide, we are faced with an obvious question. If Dr Kelly did not kill himself, then who might have been responsible for his death?
There are, it must be admitted, a number of possible suspects. In the course of a long career in the shadowy world of arms control, Dr Kelly had made powerful enemies.
Back in 1991, for example, he was part of a team that exposed Russia's tests of biological weapons for offensive purposes - a field in which they had invested huge sums of money. This could easily have sparked a desire for revenge, if not from the state itself then from individual Russians.
Dr Kelly also had intimate knowledge of biological weapons research in apartheid-era South Africa that some might have preferred not to see the light of day.It has also been suggested that he had dealings with Mossad, the Israeli secret service, about illegal bacterial weapon activity.
But it seems very unlikely that the anger of old foes would have simmered for years and then exploded just as Dr Kelly emerged in the political spotlight in 2003.Quite simply, it would qualify as an astonishing coincidence if the cause of his death were not rooted in the furore over Iraq.
At this point, it has to be asked whether there were elements in the British intelligence services, or indeed within 10 Downing Street itself, who would have wanted Dr Kelly dead.
This is a possibility I have seriously considered. But it is difficult, frankly, to think that anyone in the Government could have thought DrKelly's death to be in their interest, even were they morally prepared to bring it about.
After all, the death of Dr Kelly presented Tony Blair with his greatest political challenge, and put the political focus firmly onto the whole Iraq debacle, which cannot be where the Government would have wanted it.The more I investigated this affair, the more I realised that people who had worked with David Kelly suspected some kind of link with the Iraqis themselves.
Diplomat David Broucher told the Hutton inquiry that he interpreted Dr Kelly's remark about being found "dead in the woods" to mean that "he was at risk of being attacked by the Iraqis in some way".
Dr Kelly's friend Mai Pederson confirmed to the police that the scientist had received death threats from supporters of Saddam Hussein, who regarded him as an enemy on account of his past success at uncovering their weapons programmes.This was something Dr Kelly privately acknowledged but refused to be cowed by, in a very British, stiff upper lip kind of way.
The theory that he may have been murdered by elements loyal to Saddam is supported by Dick Spertzel, America's most senior biological weapons inspector, who worked closely with Dr Kelly in Iraq.
"A number of us were on an Iraqi hit list," he told me matter-of-factly. "I was number three, and David was a couple behind that."But Saddam loyalists are not the only Iraqis we need to consider. There are others, too, with rather closer links to the West.
Much of the information about Saddam's supposed weapons of mass destruction, on which Britain and America based their case for war, was provided by Iraqi dissidents eager to see his overthrow.
This information was sensational and, as events turned out, wildly distorted and in most regards plain false.One of the central figures here was Ahmed Chalabi, leader of the so-called Iraqi National Congress and the CIA's favourite Iraqi opposition politician.
A financier with a decidedly chequered past - he was found guilty of embezzlement and forgery after $158 million disappeared from a bank he founded in Jordan - Chalabi made no secret of his wish to drag the United States into war with Saddam and was apparently prepared to say anything to achieve that end.
A key Iraqi informer codenamed "Curveball" - who claimed to have led a team equipping mobile laboratories to produce biological weapons for Saddam, but was later entirely discredited - is believed to have been the brother of one of Chalabi's aides.
Chalabi's fingerprints can also be found on the now notorious claims by another defector that Saddam had 20 or more secret sites where weapons of mass destruction could be found. Subsequent searches showed this allegation to be utterly without foundation.
Naturally, those like Dr Kelly who, by sticking to the facts, weakened the case for invasion beforehand and discredited those who had exaggerated it afterwards, were unhelpful to Chalabi and his colleagues. The last thing they wanted was the sober truth to prevail.
Another important figure here is Iyad Allawi, leader of the Iraqi National Accord, another organisation created to oppose Saddam. Before they parted ways, he was Saddam's supporter and friend.
There are many who tell of Allawi's violent history. As a young man, he is alleged to have been present at the torture of Iraqi communists who were hung from the ceiling and beaten.
While living in London in the Seventies, he was allegedly the head of Iraq's intelligence operation in Europe, informing on opponents of Saddam who will have faced torture and death when they returned home.
Allawi went on to develop a fruitful relationship with MI6 and the CIA. After the Iraq invasion, he was appointed Prime Minister in the country's interim government - only to face allegations (which he strongly denied) that he had personally shot seven insurgents in the head with a pistol at Baghdad's Al-Amariyah security centre.
"This is how we must deal with terrorists," Allawi is alleged to have told a stunned audience of close to 30 onlookers. "We must destroy anyone who wants to destroy the Iraqi people."
The new Prime Minister's actions are said to have prompted one U.S. official to comment: "What a mess we're in - we got rid of one son of a bitch only to get another."
The Americans apparently referred to Allawi as "Saddam lite".Before the Iraq invasion, Allawi's organisation - just like Ahmed Chalabi's - was responsible for eye- catching but groundless intelligence exploited by supporters of war.
In the case of Allawi's group, it was reports passed to MI6 in the spring and summer of 2002, including the false claim that Saddam had weapons of mass destruction which he could deploy at 45 minutes' notice.
This now infamous "45-minute claim" fed through to the dossier of intelligence which was used as the justification for our involvement in the invasion of Iraq.It was this dossier, and the 45-minute claim in particular, that David Kelly challenged in his crucial interview with the BBC.
By doing so, did he sign his own death warrant?
Their adulation was such that he was being offered the rare honour of a Congressional Gold Medal.Naturally enough, Bush and his administration were hugely grateful for Blair's decision to join the United States in its invasion of Iraq.
That invasion was supposed to lead to the discovery and disposal of weapons of mass destruction (WMD) and make the world a safer place.
But as Blair was lapping up the grateful plaudits from the U.S. Congress on July 17, 2003, the man who had done more than almost any other individual on earth to contain the threat from WMD lay dead in the woods at Harrowdown Hill in Oxfordshire.
For Dr David Kelly, the UK's leading weapons inspector, there was to be no adulation, no medal, no standing ovation.
His life ended in the cold, lonely wood where he was found the next morning, his left wrist cut open, and three nearly-empty blister packs of painkillers in his jacket pocket.
His death was, of course, sensational front-page news. Dr Kelly, unknown to almost everybody at the beginning of that July, had in recent days barely been absent from media headlines.
Much to his chagrin he had been thrust into the harsh glare of publicity, accused of being the mole who expressed to the BBC deep concerns about the Government's "sexing up" of its dossier on weapons of mass destruction.
For Blair - accused of misusing, exaggerating or even inventing intelligence in order to justify the overthrow of Saddam Hussein - the stakes could not have been higher.
This was undoubtedly the greatest crisis of his premiership to date.
To add fuel to the flames, his director of communications, Alastair Campbell, had launched an unprecedented and vitriolic attack on the BBC, questioning its integrity and professionalism in the way it reported the story.
Suddenly finding himself under tremendous personal pressure, it seemed that Dr Kelly had buckled and decided to commit suicide.
That, at least, was the official version of events, as decided by the Hutton inquiry, set up by the Government with lightning speed within hours of Dr Kelly's body being found.
The media, the political establishment, indeed almost everybody accepted Lord Hutton's verdict. But the more I examined it, the more it became clear to me that Hutton's judgment was faulty and suspect in virtually all important respects.
I was not alone in these suspicions. Letters began to appear in the press from leading medical specialists, in which they queried the suicide verdict.
The letters were well argued, raising profound and disturbing questions that remain unanswered to this day.Increasingly concerned, I decided to give up my post on the Liberal Democrat front bench to look into Dr Kelly's death.
My investigations have since convinced me that it is nigh- on clinically impossible for Dr Kelly to have died by his own hand and that both his personality and the other circumstantial evidence strongly militate against suicide.
Given that his death was clearly not an accident, that leaves only one alternative - that he must have been murdered.This is not a conclusion I have come to lightly. I simply set out to examine the facts, to test the evidence, and to follow the trail wherever it took me.
The account I give in this series may not be correct in all respects, but I suggest that it is rather more credible than the verdict reached by Lord Hutton.I certainly believe there are enough doubts, enough questions, enough of a smell of stinking fish to justify re-opening this episode officially.
My investigations have been a journey into the unknown, and one that has taken many peculiar turns. Perhaps the most sinister came soon after starting my inquiries last year.
After writing a newspaper article outlining my early concerns, I found myself on a train speeding towards Exeter to see a man who had agreed to meet me only on condition of anonymity and after some rather circuitous arrangements.
These involved much complicated use of public telephone boxes to minimise the chance that his contact with me could be traced.
Finally, we talked over a glass of wine in a rather nondescript club.He told me that he had recently retired but had connections to both the police and the security services, a claim which I subsequently verified through careful checks.
Like me, he had many doubts about the true circumstances surrounding Dr Kelly's death and he had begun making his own surreptitious inquiries around Southmoor, the Oxfordshire village which was Dr Kelly's home.
Posing as a freelance journalist, he had attempted to contact the key policemen involved in investigating the case. In this he was unsuccessful but within an hour he received an unexpected return call.
The person on the other end of the line did not bother with formalities, but instead cut to the quick. How would my contact welcome a full tax inspection of his business, VAT, national insurance, the lot?
Life could be made very difficult, he was told. How did he fancy having no money?
Naturally, this prospect did not appeal, and there he left matters until, at a wedding, he chanced upon an old friend whom he described to me initially as a very senior civil servant, but later as a "spook" from MI6.
He told his friend of his interest in the Kelly affair and also of the threatening phone call he had received.His friend's reply was a serious one: he should be careful, particularly when using his phone or his computer. Moreover, he should let the Kelly matter drop.
But my contact did not do so. Two weeks later he met his friend again, this time in a pub, and pressed him on the matter. His friend took him outside, and as they stood in the cool air, told him Dr Kelly's death had been "a wet operation, a wet disposal".
He also warned him in very strong terms to leave the matter well alone. This time he decided to heed the warning.I asked my contact to explain what he understood by the terms his friend had used. Essentially, it seems to refer to an assassination, perhaps carried out in a hurry.
A few months later, I called my contact to check one or two points of his story. He told me that three weeks after our meeting in Exeter, his house had been broken into and his laptop - containing all his material on Kelly - had been stolen. Other valuable goods, including a camera and an LCD television, had been left untouched.
It was sobering to be given such a clear indication that Dr Kelly had been murdered, but the scientist himself appears to have been fully aware that his work made him a target for assassins.
British diplomat David Broucher told the Hutton inquiry that, some months before Dr Kelly's death, he had asked him what would happen if Iraq were invaded.
Rather chillingly, Dr Kelly replied that he "would probably be found dead in the woods".At the inquiry, this was construed as meaning that he had already had suicidal thoughts. That, of course, is patently absurd.
Nobody can seriously suggest that he was suicidal at the time the meeting took place - yet Lord Hutton seems to have made his mind up about the way in which DrKelly died before the inquiry even began.
The result is a series of gaping, unresolved anomalies.
Crucially, in his report, Hutton declared that the principal cause of death was bleeding from a selfinflicted knife wound on Dr Kelly's left wrist.
Yet Dr Nicholas Hunt, the pathologist who carried out the post-mortem examination on DrKelly, stated that he had cut only one blood vessel - the ulnar artery.
Since the arteries in the wrist are of matchstick thickness, severing just one of them does not lead to life-threatening blood loss, especially if it is cut crossways, the method apparently adopted by DrKelly, rather than along its length.
The artery simply retracts and stops bleeding.
As a scientist who would have known more about human anatomy than most, DrKelly was particularly unlikely to have targeted the ulnar artery. Buried deep in the wrist, it can only be accessed through the extremely painful process of cutting through nerves and tendons.It is not common for those who commit suicide to wish to inflict significant pain on themselves as part of the process.
In Dr Kelly's case, the unlikelihood is compounded by the suggestion that his chosen instrument-was a blunt pruning knife.This would only have increased the pain and would have failed to cut the artery cleanly, thereby hastening the clotting process.
Statistics bear out the extremely low incidence of individuals dying by cutting the ulnar artery, with only one recorded case in Britain during the entire year of Dr Kelly's death.
Given that the average human body contains ten pints of blood, and that about half of these must be lost before death ensues, we must also ask ourselves why there were clear signs at the postmortem-that Dr Kelly had retained much of his blood.
We cannot be sure exactly how much since, inexplicably, the pathologist's report does not provide an estimate of the residual volume, but what he did record was the appearance of "livor mortis" on Dr Kelly's body.
This purplish-red discolouration of the skin occurs when the heart is no longer pumping and blood begins to settle in the lower part of the body. But if Dr Kelly had bled to death, as we are led to believe, then significant livor mortis would not have occurred. Put simply, there would not have been enough blood in his body.
More significant still, while the effects of five pints of blood spurting from a body could not easily be hidden, the members of the search party who found his body did not even notice that Dr Kelly had apparently incised his wrist with a knife.
Their arrival was followed by that of paramedics who pointedly referred to the fact that there was remarkably little blood around the body.If the idea that blood loss brought about Dr Kelly's death is flawed, still less plausible is the suggestion that he chose an overdose to quicken his end.
Mai Pederson, a close friend of DrKelly's, has confirmed that he hated all types of tablets and had an aversion even to swallowing a headache pill.Yet we are told that he removed from his house three blister packs, each containing ten of the co-proxamol painkillers which his wife Janice took for her arthritis.
Each of these oval pills was about half an inch long. Since there was only one tablet left, the implication is that he had swallowed 29 of them. If this is right, we are being asked to believe that Dr Kelly indulged in a further masochistic act in an attempt to take his life.
A further objection is that police evidence states there was a halflitre bottle of Evian water by the body which had not been fully drunk.Common sense tells us that quite a lot of water would be required to swallow 29 large tablets. It is frankly unlikely, with only a small bottle of water to hand, that any would have been left undrunk.
Stranger still, tests revealed the presence of only the equivalent of a fifth of one pill in Dr Kelly's stomach.Even allowing for natural metabolising, this cannot easily be reconciled with the idea that he swallowed 29 of them.
Forensic toxicologist Alexander Allan told the Hutton inquiry that although the levels of co-proxamol in Dr Kelly's blood were higher than therapeutic levels, they were less than a third of what would normally be found in a fatal overdose.
Furthermore, it is generally accepted that concentrations of a drug in the blood can increase by as much as tenfold after death, leaving open the possibility that he consumed only a thirtieth of the dose necessary to kill him.
As for Dr Kelly's state of mind, in the eyes of those who knew him well he was the last person who might be expected to take his own life.A recent convert to the Baha'i faith which expressly forbids suicide, he was a strong character who had survived many difficult situations in the past.
Just a day before his 20th birthday in May 1964, his own mother had killed herself with an overdose. Though this had naturally affected him deeply at the time, there was nothing to suggest that it was on his mind at this point in his life.
His friend Mai Pederson recalled a conversation they once had about his mother's death. Would he ever contemplate suicide himself, she asked. 'Good God no, I couldn't ever imagine doing that," he is said to have replied. "I would never do it."
Later many people would conclude that the seeds of his suicide lay in his uncomfortable appearance before MPs on the Foreign Affairs Committee on Tuesday, July 15, just three days before his death.
Grilled for more than an hour during this televised hearing, he was clearly under considerable pressure and yet one journalist recalled him smiling afterwards.
By the time he gave evidence before the Intelligence and Security Committee the following day, he was even managing to crack a joke or two.His emotional state certainly did not appear to give any major cause for alarm on the morning of the Thursday he disappeared.
His wife Janice later described him as "tired, subdued but not depressed" and the e-mails he sent from his home during those hours suggested that his mood, if anything, was upbeat.
"Many thanks for your thoughts," he wrote to one colleague. "It has been difficult. Hopefully will all blow over by the end of the week and I can travel to Baghdad and get on with the real work."Indeed, so keen was Dr Kelly to get back to Iraq that he spoke to Wing Commander John Clark at the Ministry of Defence about when he could return.
A trip was booked for him the following Friday and his diary, recovered by the police, shows that the trip had been entered for that day. People about to kill themselves do not generally first book an airline ticket for a flight they have no intention of taking.
Since none of this fits the profile of a man about to commit suicide, we are faced with an obvious question. If Dr Kelly did not kill himself, then who might have been responsible for his death?
There are, it must be admitted, a number of possible suspects. In the course of a long career in the shadowy world of arms control, Dr Kelly had made powerful enemies.
Back in 1991, for example, he was part of a team that exposed Russia's tests of biological weapons for offensive purposes - a field in which they had invested huge sums of money. This could easily have sparked a desire for revenge, if not from the state itself then from individual Russians.
Dr Kelly also had intimate knowledge of biological weapons research in apartheid-era South Africa that some might have preferred not to see the light of day.It has also been suggested that he had dealings with Mossad, the Israeli secret service, about illegal bacterial weapon activity.
But it seems very unlikely that the anger of old foes would have simmered for years and then exploded just as Dr Kelly emerged in the political spotlight in 2003.Quite simply, it would qualify as an astonishing coincidence if the cause of his death were not rooted in the furore over Iraq.
At this point, it has to be asked whether there were elements in the British intelligence services, or indeed within 10 Downing Street itself, who would have wanted Dr Kelly dead.
This is a possibility I have seriously considered. But it is difficult, frankly, to think that anyone in the Government could have thought DrKelly's death to be in their interest, even were they morally prepared to bring it about.
After all, the death of Dr Kelly presented Tony Blair with his greatest political challenge, and put the political focus firmly onto the whole Iraq debacle, which cannot be where the Government would have wanted it.The more I investigated this affair, the more I realised that people who had worked with David Kelly suspected some kind of link with the Iraqis themselves.
Diplomat David Broucher told the Hutton inquiry that he interpreted Dr Kelly's remark about being found "dead in the woods" to mean that "he was at risk of being attacked by the Iraqis in some way".
Dr Kelly's friend Mai Pederson confirmed to the police that the scientist had received death threats from supporters of Saddam Hussein, who regarded him as an enemy on account of his past success at uncovering their weapons programmes.This was something Dr Kelly privately acknowledged but refused to be cowed by, in a very British, stiff upper lip kind of way.
The theory that he may have been murdered by elements loyal to Saddam is supported by Dick Spertzel, America's most senior biological weapons inspector, who worked closely with Dr Kelly in Iraq.
"A number of us were on an Iraqi hit list," he told me matter-of-factly. "I was number three, and David was a couple behind that."But Saddam loyalists are not the only Iraqis we need to consider. There are others, too, with rather closer links to the West.
Much of the information about Saddam's supposed weapons of mass destruction, on which Britain and America based their case for war, was provided by Iraqi dissidents eager to see his overthrow.
This information was sensational and, as events turned out, wildly distorted and in most regards plain false.One of the central figures here was Ahmed Chalabi, leader of the so-called Iraqi National Congress and the CIA's favourite Iraqi opposition politician.
A financier with a decidedly chequered past - he was found guilty of embezzlement and forgery after $158 million disappeared from a bank he founded in Jordan - Chalabi made no secret of his wish to drag the United States into war with Saddam and was apparently prepared to say anything to achieve that end.
A key Iraqi informer codenamed "Curveball" - who claimed to have led a team equipping mobile laboratories to produce biological weapons for Saddam, but was later entirely discredited - is believed to have been the brother of one of Chalabi's aides.
Chalabi's fingerprints can also be found on the now notorious claims by another defector that Saddam had 20 or more secret sites where weapons of mass destruction could be found. Subsequent searches showed this allegation to be utterly without foundation.
Naturally, those like Dr Kelly who, by sticking to the facts, weakened the case for invasion beforehand and discredited those who had exaggerated it afterwards, were unhelpful to Chalabi and his colleagues. The last thing they wanted was the sober truth to prevail.
Another important figure here is Iyad Allawi, leader of the Iraqi National Accord, another organisation created to oppose Saddam. Before they parted ways, he was Saddam's supporter and friend.
There are many who tell of Allawi's violent history. As a young man, he is alleged to have been present at the torture of Iraqi communists who were hung from the ceiling and beaten.
While living in London in the Seventies, he was allegedly the head of Iraq's intelligence operation in Europe, informing on opponents of Saddam who will have faced torture and death when they returned home.
Allawi went on to develop a fruitful relationship with MI6 and the CIA. After the Iraq invasion, he was appointed Prime Minister in the country's interim government - only to face allegations (which he strongly denied) that he had personally shot seven insurgents in the head with a pistol at Baghdad's Al-Amariyah security centre.
"This is how we must deal with terrorists," Allawi is alleged to have told a stunned audience of close to 30 onlookers. "We must destroy anyone who wants to destroy the Iraqi people."
The new Prime Minister's actions are said to have prompted one U.S. official to comment: "What a mess we're in - we got rid of one son of a bitch only to get another."
The Americans apparently referred to Allawi as "Saddam lite".Before the Iraq invasion, Allawi's organisation - just like Ahmed Chalabi's - was responsible for eye- catching but groundless intelligence exploited by supporters of war.
In the case of Allawi's group, it was reports passed to MI6 in the spring and summer of 2002, including the false claim that Saddam had weapons of mass destruction which he could deploy at 45 minutes' notice.
This now infamous "45-minute claim" fed through to the dossier of intelligence which was used as the justification for our involvement in the invasion of Iraq.It was this dossier, and the 45-minute claim in particular, that David Kelly challenged in his crucial interview with the BBC.
By doing so, did he sign his own death warrant?
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