Diary entries undermine Hoon claim that there was no conspiracy to reveal Dr Kelly

Two Alastair Campbells were at the Hutton inquiry yesterday. There was Dr Jekyll in the witness stand, giving another measured if slightly less assured performance. Then Mr Hyde who emerged in remarkable extracts from his diary, handed to the inquiry and published on its website.

The language in the diary was much more stark than in the courtroom. It might have been abbreviated and hastily written, as Mr Campbell told the inquiry, but few who know him would doubt that this was the real Alastair Campbell.

After David Kelly admitted he had met the BBC journalist Andrew Gilligan, Mr Campbell's arch-enemy, he noted colourfully: "It was double-edged but GH [Geoff Hoon] and I agreed it would fuck Gilligan if that was his source."

Downing Street's outgoing director of communications did not mince his words. Mr Hoon's "initial instinct was to throw the book at him" [Dr Kelly]. When Tony Blair "backed off" from telling the BBC the Government knew Mr Gilligan's source, Mr Campbell wrote: "GH and I felt we were missing a trick."

The diary highlights Mr Campbell's determination to secure victory over the BBC. He was busily briefing newspapers that the BBC "would eventually apologise" -- which it did not. "My worry was that I wanted a clear win and if they presented it as a draw that was not good enough for us," he wrote. His mindset is revealing, and may explain why Number 10 did not take the opportunities that arose for a truce with the BBC, notably after the Commons Foreign Affairs Committee cleared Mr Campbell of Mr Gilligan's charge that he "sexed up" the Government's dossier on Iraqi weapons.

The most damaging extract of the diary is when Mr Campbell said: "The biggest thing needed was the source out" -- in other words, he wanted Dr Kelly unmasked because, he hoped, this would discredit Mr Gilligan.

His recollections are potentially disastrous for Mr Hoon, who insisted repeatedly in his evidence earlier yesterday that there was no conspiracy by the Government to leak Dr Kelly's name. This was undermined by Mr Campbell, who wrote: "GH and I both wanted to get the source up." At another stage, "GH wanted to get up source." He added: "GH said he was almost as steamed up as I was."

In contrast, Tony Blair emerges much better from the diary; he is more cautious about using Dr Kelly to further the dispute with the BBC. While Mr Campbell and Mr Hoon were chomping at the bit to unmask Dr Kelly, "TB was nervous about it" .

The Prime Minister "wanted natural justice" and "didn't want to push the system too far". Remarkably, when Mr Campbell could not persuade Mr Blair that the BBC should be tipped off that the Government knew its source, he suggested Mr Hoon try to change his mind.

In my experience, allegations of conspiracy by governments of any colour are often misplaced; the "cock-up theory" is less interesting to the media but is often the real explanation. But yesterday Jeremy Gompertz, the QC representing Dr Kelly's family, built a powerful case for a conspiracy to bring the weapons expert's name into the public domain when he cross- examined Mr Hoon.

Firstly, there was the statement issued by the Ministry of Defence that an anonymous official had come forward to say he had met the BBC journalist Andrew Gilligan. Mr Hoon admitted this was bound to excite the media into finding out the official's identity, as indeed it did.

Second, the MoD produced a "question and answer" briefing for its press officers, under which they would confirm Dr Kelly's name if it was put to them by a journalist.

Third, there were the additional clues to Dr Kelly's identity offered by Tom Kelly, the Prime Minister's official spokesman, who will be asked about his briefings when he is recalled to the inquiry today.

Denying a conspiracy, Mr Hoon said there was "not the slightest shred of evidence for that assertion".

But Mr Gompertz won the argument that it seemed more conspiracy than cock-up. Lord Hutton leant forward and, in one of his rare but telling interventions, repeated the "conspiracy" question.

Perhaps we should not read too much into Lord Hutton's words. But I would not be surprised if the senior law lord does not focus very hard on this point when he produces his inquiry report in November.

I am not alone in thinking this. Ministers expect the Government to be criticised for failing in their "duty of care" to Dr Kelly, and for the fateful decision to push him into the public spotlight.