Already the Hutton inquiry is making life uncomfortable for the Government

The insulting suggestion by government spin doctors that Dr Kelly was a minor functionary has already been disproved

Yesterday, Tony Blair's premiership, along with the reputation of his Government, was put on trial in Court 73 of the Royal Courts of Justice. Lord Hutton's inquiry unwittingly holds the key to the date at which the leadership of the Labour Party will be changed, to the ambitions of Gordon Brown and, perhaps, to the outcome of the next general election. For the first time during his premiership, Mr Blair is not in the driving seat and no amount of spin or control-freakery will be able to dictate the proceedings.

The first witness, Terence Taylor, described Dr Kelly as his "scientific and technical mentor" and established beyond any doubt the extent to which Dr Kelly was the leading expert in the field of Iraq's weapons of mass destruction. So the original insulting suggestion by government spin doctors that he was merely a middle-ranking official - a minor functionary - has already been disproved. It is also clear that, contrary to government briefings, Dr Kelly most certainly did have access to sensitive intelligence material.

And the admission by Martin Howard, the deputy chief of defence intelligence, indicates that concerns over the wording of the September dossier were also expressed by at least two other officials at the Ministry of Defence. But there will be some relief in Downing Street at the view of the Cabinet Office official Julian Miller - the chief of the assessment staff - that this dossier had not been "transformed" on the orders of Alastair Campbell. The attempt, however, to suggest that Dr Kelly was not authorised to give informal press briefings by the MOD personnel officer Richard Hatfield is bound to be ferociously challenged when BBC journalists give their evidence.

Andrew Gilligan will, crucially, give his version of events to Lord Hutton today, and the next two months of testimony from all the witnesses will be seized on by opinion- formers, more for evidence to help to decide the real question of whether we went to war against Iraq on a false prospectus then to decide who may have driven Dr Kelly to his death.

Indeed, what is already apparent is that Lord Hutton's inquiry is following a well-established historical precedent. In most inquiry and court proceedings - and select committee proceedings - the evidence sessions themselves may have as great an impact on the media's interpretation, and on the wider court of long-term public opinion, as the final report. Few will have read or remembered the ultimate conclusions of the Foreign Affairs Selection Committee report, published last month. But we still remember the aggressive and macho way in which Alastair Campbell used the proceedings to launch his attack on the credibility of Andrew Gilligan. And we vividly recall the generally nervous disposition of Dr Kelly during the hostile questioning by MPs.

The report itself, published after the evidence sessions, is already gathering dust and has had far less impact than the demeanour and behaviour of these two witnesses during their testimonies. The repeated broadcasts in newsclips of the question-and-answer sessions by the main protagonists have played a far greater part in setting the national mood than the findings of the MPs. In fact, the principal conclusion of the report - that Dr Kelly could not possibly have been Mr Gilligan's source for his broadcast - appears actually to have been spectacularly wrong.

So in the court of public opinion, and in the eyes of the media, the transcripts of the array of witnesses being cross-examined will be as important as the pages of Lord Hutton's final report. It recalls the circumstances leading up to the publication of Lord Scott's inquiry in the early 1990s over the arms-to-Iraq affair. The oral evidence from the late Alan Clark when he used his memorable phrase of being "economical with the actualité'' defined the whole sorry affair. When the report was dissected afterwards, Mr Clark's one-liner, during the proceedings, remained as much the defining basis on which the public decided that there had been a scandal.

Similarly the original libel case brought by Jeffrey Archer against the Daily Star is remembered not so much for the outcome, resulting in £500,000 damages that he wrongly secured from that newspaper, but for the testimony of Mary Archer and the "fragrant'' impression she made on court - at least in the eyes of the judge and the media.

The final conclusions of Lord Denning's report on the Profumo affair have long since been forgotten. But, again, the evidence given by Christine Keeler and Mandy Rice-Davies during the proceedings of the trial of Stephen Ward lives on to a much greater extent in the public memory. Press reports, 40 years on, still tend to dwell more on the courtroom drama, at the point when the prosecution alleged that Rice-Davies had received money from Lord Astor for sex. When she was told that Lord Astor had ever denied sleeping with her, she uttered the immortal line: "He would, wouldn't he?''

The basic question - "Who killed Dr Kelly?'' - is therefore bound to be answered elsewhere: at the official inquest where presumably the obvious conclusion is likely to be suicide. So it is unlikely that key witnesses will be specifically accused of having blood on their hands. But political blood could still be spilt during the testimonies, and Geoff Hoon, the Secretary of State for Defence, may now have the power to inflict as well as endure pain.

Although he has been accused of being crass over the personal decision to go on holiday during Dr Kelly's funeral, it looks as though he could be as much the victim of the story as he has been painted the villain. Yesterday's testimony as to how Dr Kelly's name came into the public domain, given by Mr Hatfield cannot be fully assessed until we hear from Mr Hoon and his Permanent Secretary about their discussions with Downing Street over the "outing'' of Dr Kelly.

Mr Hoon is entitled to feel hard done by, having suffered the same kind of negative "Whitehall sources'' suggesting that: "Hoon will be the fall guy for the Government. He is going to be hung out to dry in the hope his resignation will get Tony Blair off the hook. Nobody believes that Hoon was the one behind the leaking of Dr Kelly's name, that would never have been done without Downing Street's say so, but Hoon is expendable while the Prime Minister isn't.''

Mr Hoon was already feeling aggrieved when he was passed over for promotion during the summer reshuffle. If he now finds that he is to become the latest victim in the battle to save the Prime Minister's reputation, he might just decide that he has nothing to lose by shedding more light on the murkier workings of this Government than would be comfortable for Downing Street. Mr Hoon's testimony may turn out to be more damaging for Mr Blair than the report itself, particularly if he were to imply - in the spirit of the military culture of his department - that "I was only obeying orders''.

mrbrown@pimlico.freeserve.co.uk