One of Ming Campbell’s more light-hearted legacies to his party was the elevation to the position of Shadow to the Chancellor of the Duchy of Lancaster of Norman Baker, the MP for Lewes. In fact Mr Baker’s job represented a repromotion, since he had previously been environment spokesman for the Lib Dems, but had decided to give the post up to pursue other matters. The nature of those other matters became clear at the weekend with the serialisation of his book, entitled, The Strange Death of David Kelly, or, as the headline put it, “Why I know weapons expert Dr David Kelly was murdered, by the MP who spent a year investigating his death.”

This charge, from a senior MP in an influential newspaper, is sensational in the truest sense of that word. Surely, the reader may be entitled to imagine, such an accusation would not be made lightly and that Mr Baker will have done his homework. His accusations, therefore, deserve scrutiny.

Mr Baker’s initial objections to the verdict of suicide on Dr Kelly were both intuitive and practical. Mr Baker simply doesn’t believe that the senior arms inspector was suicidal, since he was a “strong character who had survived many difficult situations in the past”, including the self-destruction by overdose of his own mother when he was 20. And Mr Baker worries too about a series of what he believes are discrepancies about the finding of Dr Kelly’s body on Harrowdown Hill in July 2003. Was he wearing a coat when found? And had the body been moved?

More practically Mr Baker sides with a small number of medical people who have expressed their belief that Dr Kelly could not have died as the pathologist said he did. The combination of ingesting 29 co-proxamol tablets, and cutting across the ulnar artery in the left wrist, means it is, in Mr Baker’s words, “nigh-on clinically impossible for Dr Kelly to have died by his own hand”.

But soon Mr Baker’s early doubts of suicide are turned into certainties of foul play by a couple of gods that yank themselves out of the machine. A man in Exeter “who had agreed to meet me only on condition of anonymity and after some rather circuitous arrangements” tells the MP of encountering an old spook colleague in a pub who in turn says that Dr Kelly’s death had been “a wet operation, a wet disposal”. Three weeks later Exeter Man loses all his Kelly material when his computer is stolen in a mysterious burglary.

A second anonymous source who meets Mr Baker in the Commons goes quiet, fails to supply promised information and is then “subjected to an horrific attack by an unknown assailant, the full details of which he has asked me not to reveal”. But Mr X does confide that the murderers of the weapons inspector were anti-Saddamite Iraqis dangerously embarrassed by Dr Kelly’s scepticism about one of their main tips to British Intelligence – that Iraq had WMD ready to go within 45 minutes. Mr Baker was told that these exiles nabbed Dr Kelly when he went for a walk, injected him in the bottom with something to keep him quiet and then killed him by some unknown method. Mr Baker believes that it is likely that the British authorities, realising what had happened, doctored the body to make it all look like suicide.

If some of this sounds unplaceably familiar to readers over 35, I may be able to help you. In March 1984 an elderly rose grower, Hilda Murrell, was abducted from her Shrewsbury home and later found dead in a small copse some miles away. The police said it was a bungled burglary, but some in Shrewsbury’s anti-nuclear community suspected a political motive. Miss Murrell was about to publish a paper opposing further development of nuclear power.

These campaigners, and interested journalists, pointed out the many anomalous features of the case, including the time it took to discover the body, the implausibility of a burglar choosing to drive his victim out of town in broad daylight, and the condition of the telephone wire in her house. World in Action on ITV devoted a programme to the possibility that Miss Murrell was the victim of a political murder.

That December the Labour MP Tam Dalyell announced in the Commons that he had been told by two anonymous sources that Miss Murrell had been killed in a botched break-in by people looking for “ Belgrano-related documents” left there by her nephew, who had been in Naval Intelligence at the time of the 1982 sinking of the Argentine battlecruiser. “The searchers were members of British Intelligence, I am informed,” Mr Dalyell said.

There the accusation lay for more than 20 years – with many playwrights and journalists believing that the Thatcherite State was quite capable of such murderousness – until new DNA evidence and a cold-case review established who the Murrell murderer was. He turned out to have been, at the time of the killing, a 16-year-old petty criminal called Andrew George, who lived in a local care home. In 2005 he was imprisoned for life.

The Dalyell idea of a Murrell conspiracy mirrors in almost every important detail the Baker idea of the Kelly murder, with the dismissal of the “official version” as somehow deficient, and in the build-up of anonymous information. And, like Mr Baker’s accusations, Mr Dalyell’s speculations were not victimless. As far as I know Mr Dalyell has never apologised to those police officers, Home Office staff and secret service personnel whom he effectively slandered and whose time he squandered. Mr Baker happily puts the Thames Valley Police, the pathologists and (by implication) Tony Blair in the frame, and once more causes upset to the Kelly family.

If Mr Baker were himself to be Bakered, then he might be challenged to tell his constituents on whose behalf he has wasted a year concocting absurd accusations. Does he think that, two months after the fall of Saddam, their country in turmoil, Iraqi exiles were wandering round the English countryside bumping off scientists who believed – as Dr Kelly did – that Saddam possessed WMD?

But there is a way to settle this. Since the fearless Mr Baker believes it is impossible to die in the way Dr Kelly is supposed to have done, then he should be able to meet the simple challenge of himself taking 29 co-proxamol tablets and then slitting his left ulnar artery. Unless, of course, he secretly suspects that the next day Nick Clegg or Chris Huhne would find themselves looking for a new Shadow to the Chancellor of the Duchy of Lancaster.

David Aaronovitch will be speaking on Democracy and its Discontents at the Battle of Ideas this Sunday, October 28