The BBC and Andrew Gilligan have some tough questions to answer after yesterday's explosive statement.
When the Government revealed on 8 July that a member of the Ministry of Defence staff had met Gilligan in a central London hotel, the BBC responded by saying: "The description ... does not match Mr Gilligan's source in some important ways."
Was the corporation guilty of deliberate obfuscation? The truth is more alarming. The corporation's senior news executives did not know the identity of Gilligan's source when his initial "sexing up" allegation against Alastair Campbell was broadcast.
They still did not know on the evening of 8 July. That evening, Richard Sambrook, the head of BBC news, told me in an e-mail that he did not think the individual fingered by the MoD was "our man".
I am certain that this was his genuine opinion. But the implication is that the BBC went to war with the Government while unsure of its own ground.
This matters. Scant doubt can remain that the Government sent British forces into battle on the basis of exaggerated assessments of the threat posed by Saddam Hussein. Gilligan's reporting has done as much as the work of any other journalist to draw that truth to public attention. But the implication of his 29 May report, defended by the director general and the BBC governors against criticism from the Government and Parliament, was that this had been done deliberately and that the BBC knew who was responsible.
That now appears to be untrue. Dr David Kelly was not a member of the security services. He did not attend relevant meetings of the Joint Intelligence Committee. He was not involved in the compilation of the "dodgy dossiers".
It is not enough to believe that the Government has done wrong and deserves everything now being thrown at it. The credibility of Gilligan's reporting was substantially enhanced because it was broadcast by the BBC. If that too was "sexed up", then the corporation has damaged its own reputation.
When a journalist receives a briefing as significant as the one Gilligan received from Dr Kelly, there is often tension between proving that the source is credible and protecting his identity. Gilligan's duty as a reporter was to maintain Dr Kelly's anonymity. His employers had no less a duty to satisfy themselves that every syllable of his account was objectively accurate and properly sourced. That was the procedure I was taught when I worked for the BBC. It is difficult to understand how they could do that without knowing more about Dr Kelly's role and responsibilities than it is now clear they did know.
Either Mr Gilligan did not tell them the whole story or he did and BBC news executives chose an exciting exclusive over rigorous accuracy. Whichever proves to be the truth is highly disturbing.
Unless Mr Gilligan and the BBC can provide convincing explanations for their conduct on and since 29 May they will lend succour to Blairite loyalists and their allies in the press who have sought to depict the BBC as promoting a vendetta against Alastair Campbell and the Prime Minister. That was always a preposterous allegation. But the BBC must prove it to be so. It can no longer rely on trust alone.
Tim Luckhurst worked on the 'Today' programme for five years and is the author of 'This is Today, A Biography of the Today Programme' (Aurum Press)