On trial: the Prime Minister, his government, the BBC and the security services

Politically, if not technically, the Government goes on trial in the Royal Courts of Justice today. It's not too much to say that the fate of Tony Blair's Government now lies in the hands of the sober-suited, 72-year-old Ulsterman who will this morning start hearing the first testimony in his enquiry into the events which led to the death of David Kelly.

Lord Hutton, who until last month was almost unknown outside his native Northern Ireland, will for the next few weeks become the most pivotal as well as the most interesting public figure in the country. A key part of Lord Hutton's daunting task will be to establish what role, if any, the Government's conduct played among the factors which led to Dr Kelly's decision to take his life. And the judge has the potential to bring down cabinet ministers, senior officials and even, if his conclusions are devastating enough, the Prime Minister himself.

It's not the first time an eminent senior judge has been called in to examine the background to a crisis in government confidence and credibility. In another torrid political summer 40 years ago, Lord Denning was commissioned by a beleaguered Harold Macmillan to enquire into the Profumo affair. That affair also involved, besides a sex scandal, the intelligence services, fundamental issues of national security, and eventually a suicide, though of the osteopath Stephen Ward, a man who, to put it mildly, had none of Dr Kelly's outstanding reputation as a public servant.

Sceptics of the present process will draw unpalatable conclusions from the Denning precedent, though his enquiry, unlike Lord Hutton's, was secret. The Denning report was a best-seller when it was published in October 1963, as Lord Hutton's will be. But the Denning report was widely criticised as a whitewash, not least because it laid most of the blame on the dead man-who had introduced Jack Profumo to Christine Keeler, and largely cleared the Government.

The hunch that despite all the differences between the two cases, history might repeat itself, has been sharpened by the infamous depiction from inside Downing Street of Dr Kelly as a "Walter Mitty". The possibility the phrase was intended to underline is that Dr Kelly went well beyond what he knew, and the facts, in linking No 10 to the content as well as the presentation of the dossier used to persuade the British public that Saddam Hussein represented a present and serious danger to Western interests. If Dr Kelly was, in this respect, unreliable then it is not only convenient to the Government. It is also convenient to the BBC by reinforcing its argument that Mr Gilligan accurately reported his source, even when he went further than he had on the Today programme and blamed Alastair Campbell in his Mail on Sunday article for the "sexing-up" of the dossier. Neither side is necessarily damaged (and the BBC is significantly assisted) if the speculation is borne out that the tape of conversations with Dr Kelly by the experienced BBC Newsnight journalist Susan Watts contain most of what was in Mr Gilligan's report. The dead man gets the blame for a story which the Government will insist was untrue and the BBC will insist, at the very least, was transmitted in good faith.

But the first is a matter of simple politics. For the Government to concentrate its fire on a man who cannot answer back carries considerable risks for its reputation. The second is that the issues themselves are less clear-cut than the "Walter Mitty" strategy allows. A great deal has been rightly said about the narrowness of Lord Hutton's remit. And he certainly isn't there to assess the credibility of the intelligence, much less the legal and political basis for going to war.

But it's hard to see how he can avoid any discussion of what really seems to have concerned Dr Kelly, and Ms Watts reported judiciously in early June, the pressure he appears to have believed the intelligence community was put under to come up with conclusions which would make the case for war. This goes beyond a wrong inference that Mr Campbell simply inserted a reference to the claim that Saddam could deploy his weapons within 45 minutes, which Ms Watts reported her source as accepting came from the intelligence services. On the one hand, No 10's strongest suit is that Sir Richard Dearlove, the head of MI6 and John Scarlett the chairman of the Joint Intelligence Committee signed off the dossier, making it much more difficult for the services to complain about its contents. On the other, Dr Kelly's apparent concerns that they may have succumbed to pressure from No 10 (and Mr Campbell was chairing a committee responsible for the dossier) raises concerns Lord Hutton may find difficult to ignore.

A great deal depends on him. And the culture of the senior judiciary, and in particular its relationship with governments, has changed greatly since Lord Denning's time. The remorselessly searching enquiry by Lord Hutton's fellow law lord, Sir Richard Scott, into arms for Iraq under John Major, may be a more relevant, as well as a more recent, precedent.

Lord Hutton, as a former lord chief justice of Northern Ireland, has at least as visceral understanding of the demands of the state as Lord Denning had. But his reputation as a judge, apart from being very high, gives little clue about how he will proceed. Yes, he criticised his colleague Lord Hoffman for voting for General Augusto Pinochet's extradition without declaring his membership of Amnesty International. But as a Protestant in daily contact with the threat the IRA posed to himself and his fellow judges, in 1992 he still acquitted the former republican prisoner Patrick Nash - whom he branded an "accomplished liar" - because he could not be sure an RUC beating had not secured his confession.

Nor did he flinch from resisting establishment pressure when he dismissed the British Army appeal against the conviction of Private Lee Clegg for shooting a teenage joyrider.

So far, he has proceeded with exemplary wisdom. By holding the enquiry in public but not on television he has avoided the danger that the public will judge the credibility of witnesses by their ability to perform. It's hard, given the relevance of Dr Kelly's grilling by the Foreign Affairs Select Committee to his state of mind before his death, to imagine he will not consider recommending that it in future the committee does likewise; and becomes less a platform for grandstanding and more a forum for establishing truth.

Nor is his job merely to adjudicate between the BBC and the Government. He will surely have to assess, among many other things, the severity and propriety of the pressures applied on Dr Kelly by the Ministry of Defence in several days of interviews after the weapons scientist identified himself as having talked to the BBC journalist Andrew Gilligan. Mr Gilligan then reported that Mr Campbell had been involved in "sexing up" the intelligence dossier. And secondly, and perhaps even more sensitively, Lord Hutton will try to find out how high up, and how centrally, lay the responsibility for the process which led to the revelation of Dr Kelly's name on 10 July.

In 1963, when Lord Denning reported on John Profumo, the Macmillan government was already tottering. A plausible, even exciting, alternative government was at hand. That is not the case now. It seems highly possible the enquiry will lead to the expiatory sacrifice of the chronically tone-deaf Defence Secretary, Geoff Hoon, and perhaps of Mr Campbell. But Mr Blair may well recover politically from the deeply symbolic blow that would have been dealt New Labour and its fixation with media coverage by Dr Kelly's death. The Prime Minister and his allies have strongly indicated he believes he has nothing to fear. It could be difficult, if not impossible, to ascribe blame for a tragic death which may well not have a single cause.

But for the inquiry to mark the beginning of an era in which Mr Blair starts to regain the public trust forfeited since the war on Iraq, Lord Hutton will have to do more than clear Mr Blair of direct involvement in the naming of Dr Kelly, or of overt interference in the intelligence assessment which led to the September dossier. He, and perhaps Mr Blair in his testimony, will have to show beyond reasonable doubt that his is a government which has not subordinated its respect for the proprieties of public and democratic life to its own mission to do what at any given moment it deems necessary, desirable or expedient. From today, Lord Hutton holds the future, long- as well as short-term, of the Blair Government in his hands.

THE KEY QUESTIONS

* Who, in Government, took the decision to disclose David Kelly's identity to the media?

* What took place in the communications over the affair between various parts of the Government including Downing Street, the MoD, and the Foreign Office?

* What knowledge did Tony Blair, Geoff Hoon and Alastair Campbell have about the decision to disclose Dr Kelly's identity?

* Was Dr Kelly just a "middle-ranking technical official" as the Government claims, or one of the country's foremost authorities on biological weapons?

* What role did Dr Kelly have in producing the Iraq dossier, and what were his links to intelligence?

* What pressure was put on Dr Kelly by the Government?

* Did the Government mislead the public about Dr Kelly?

* Did Dr Kelly claim the Government wanted to insert the 45-minute claim? If he did, was this true?

* How much control did Mr Blair and Mr Campbell have over the MoD in the affair?

* What were the circumstances behind the BBC broadcast by Andrew Gilligan?

* Why did the BBC refuse to name Dr Kelly as its source for so long?

* What did Dr Kelly's family know about what was going on?

* What was Dr Kelly's mental and physical state in the days before his death?

* Why did Dr Kelly kill himself?