No one, not even the Prime Minister, appears to have read the legendary Campbell Diary, though its existence has yet to be denied.
If published, it promises not only to make Alastair Campbell a rich man, but to provide a priceless source of material on the rise of New Labour.
Tony Blair has few genuinely close friends in politics, and has had public falling-outs with almost all of them. Peter Mandelson has left the Cabinet, twice; the Prime Minister has clashed semi-publicly with Gordon Brown in the past three months over foundation hospitals and top-up fees; and last week he distanced himself from his old pupil master, the Lord Chancellor, Lord Irvine, over jail sentences for burglars.
Despite the rumours, there has never been any public show of disagreement with Mr Campbell, who has been at Mr Blair's side almost from the day when he was elected leader of the Labour Party in 1994. They have known each other for about 15 years.
There was a difficult patch last month when Cherie Blair decided that her dealings with the conman Peter Foster were nobody else's business and would not discuss them even with Campbell, with disastrous results for Downing Street's relations with the media.
Mrs Blair's most stalwart ally is Sally Morgan, a Labour peer and one of the most experienced political advisers in Downing Street.
She is reputed to think that the combative Mr Campbell gets too engaged in fighting battle with journalists of whom he disapproves, when he should be concentrating on protecting those in Downing Street who do not deal directly with the media.
Baroness Morgan's views are doubtless coloured by own experience of being exposed in the Daily Mirror for sending her children to private school. She is said to think that her family were innocent bystanders in a war between Mr Campbell and the Mirror's editor, Piers Morgan.
Rumours of a Blair-Campbell rift arising from the "Cheriegate" affair may have motivated certain senior people in Whitehall to choose this moment to strike against the feared Campbell diary.
Diaries and memoirs have become a sensitive issue in government circles. A woman working for Downing Street's media monitoring unit was discouraged from attending Mr Campbell's 8.30am meetings because she was thought to be taking notes with the intention of publishing.
Martin Sixsmith, the former communications director at the Department of Transport, severely embarrassed the Government by producing notes he had taken of meetings with ministers and civil servants. Mo Mowlam, the former Secretary of State for Northern Ireland, and Keith Hellawell, the former "drugs tsar", have published revealing memoirs of their time in office.
But the assumption that recent problems have opened a rift between the Prime Minister and his communications director seems to have been fuelled by wishful thinking. One official who sees them working insisted yesterday that their relationship is "excellent". Mr Campbell can always leave, with the guarantee that he will make more money outside No 10 than he does now.
One certainty is that his diary – if it exists – is not stored on a computer, but will be written in Mr Campbell's longhand. He has had an almost neurotic aversion to computers since he was a young journalist writing a novel on one of the early Amstrad machines.
Mr Campbell had completed the work when it vanished from the computer's memory – causing him so much stress that he lay down on his bed and covered his head with a duvet. Calling in technicians was of no avail – that first book-length Campbell work was lost for ever. There are Whitehall mandarins who wish the second would go the same way.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies