Reputations on the line as the British establishment goes on trial

Ministers, civil servants and journalists alike will have to explain themselves to a judge who is not likely to be overawed by any of them. Andy McSmith analyses just what is at stake and for whom

When they all assembled in Court 73 - the High Court judge, the clerks, attendants, onlookers and some of the most expensive wigs in town - it was finally brought home how serious this quarrel between a BBC journalist and a former tabloid journalist had become.

The British establishment is peering into its own entrails. The parties involved in this dispute are some of the most respected institutions in the land - Downing Street, the Ministry of Defence, the House of Commons, the BBC - which among them appear to have driven an eminent scientist to suicide.

It could be an occasion when some famous biters will find themselves being bitten, because Lord Hutton is not likely to be overawed by the fame and importance of those paraded before him.

The main focus of public interest will doubtless be on how the Government's reputation emerges from the four-month inquiry, with the moments of high theatre being the appearances by Tony Blair himself, his director of communications, Alastair Campbell, and the Defence Secretary, Geoff Hoon.

There may also be awkward questions asked of senior officials in the Ministry of Defence.

But it will not simply be a case of the Government being on trial. Journalists are also going to have to defend themselves in front of a judge who may take a dim view of some of the ways they gather and use information. Though Andrew Gilligan, defence correspondent for BBC's Today programme, is the most exposed, he may not be the only journalist who runs into criticism.

And Dr David Kelly will be a silent, invisible presence through every day of this hearing, with his posthumous reputation also at stake.

The hearing will be in two parts. In the first half, over the summer, witnesses will be questioned only by James Dingemans, Lord Hutton's senior counsel, whose job is to elicit information in a "neutral" way. They will include Tony Blair. The witnesses with something to worry about will be those called back a second time, in the autumn, to face cross-examination by other lawyers.

Alastair Campbell will come under heavy fire from Andrew Caldecott, the QC retained by the BBC. The corporation has not retreated an inch from its original allegation that information provided by the intelligence service was "made sexier", on Downing Street's instructions, as the Government prepared public opinion for war with Iraq. Mr Blair and his staff have been equally consistent in denying the allegation.

Alastair Campbell, who has fought his battle on his own and the Prime Minister's behalf, will have to be careful how he behaves in court. He has a combative manner when challenged, showing little deference for those who cross him, regardless of their status. This may produce results when he is bending civil servants to the Prime Minister's will, or defending himself before a Commons committee, or berating journalists, but High Court judges do not like being spoken to in that manner.

The last time Mr Campbell was in the Royal Courts of Justice was in 1996, when he was a defendant in a libel case brought by the former Tory MP Rupert Allason, arising from his time as political editor of the Daily Mirror. His excessive self-confidence did not go down too well with the judge, Sir Maurice Drake, who said: "I did not find Mr Campbell a wholly satisfactory or convincing witness. He did not impress me as a witness in whom I could feel 100 per cent confident."

The judge demonstrated that he did not have a general animus against journalists by going on to describe Mr Campbell's co-defendant, another ex-Mirror journalist, as "an impressive witness whose evidence had a firm ring of truth". I know, because I was that co-defendant.

However, unlike some other witnesses at the inquiry, Mr Campbell is not fighting to save his job. He wants to leave Downing Street anyway, but he wants to go with his reputation intact, which is why he has fought so ferociously to try to force the BBC to retract the allegation that he tampered with intelligence reports on Iraq.

One of the many ironies of this complicated story is that Campbell's name was never mentioned in any of the reports broadcast by the BBC based on information given to its journalists by Dr Kelly. Instead, his name appeared in an article in the Mail on Sunday by Mr Gilligan, which also gave details which helped to convince the Government that Dr Kelly was the source of Mr Gilligan's allegations.

Mr Caldecott's brief is to defend everything Mr Gilligan broadcast or wrote, which will involve negotiating some tricky obstacles. There is, for instance, the fact that Susan Watts and Gavin Hewitt, the other BBC journalists who spoke to Dr Kelly and who will be called before Lord Hutton, did not make any allegation that involved Mr Campbell personally. There is also the letter Dr Kelly wrote to his line manager in the MoD, alleging that Mr Gilligan "considerably embellished my meeting with him", which would suggest that to defend its own journalist, the BBC will have call Dr Kelly's reliability into question.

It is understood that the BBC's case will centre on a number of "untruths" told by Dr Kelly. This could start a conflict between the BBC and the Kelly family, which will be represented at the hearing by a QC, Jeremy Gompertz.

The Ministry of Defence, and the Defence Secretary, Geoff Hoon, are obviously in the firing line as Lord Hutton probes into what drove Dr Kelly to suicide. Mr Hoon could be the sacrificial victim, forced to resign when details emerge of how Dr Kelly's name became public, against his stated wishes. Whether the MoD knew he was suffering from a heart condition has yet to be established.

But we now know that - contrary to rumour - Dr Kelly was not whisked away to an MoD "safe house" during the last days of his life, but was at various addresses in Weston-super-Mare and Cornwall.

His family will give evidence about why he did not want to go home, but one explanation that leaps to mind is that he was afraid of the journalists lurking on his doorstep.

Lord Hutton's inquiry is not a court of law. Witnesses will be asked rather than compelled to give evidence; the rules for examining them will be strictly controlled; and there will be no formal verdict at the end. And yet for some of the people involved, the stakes are almost as high as if it were a criminal trial, because their reputations and/or careers could be ruined by it.