The latest twist in the saga over Dr David Kelly brings into focus the murky world of the "off-the-record" briefing.
Tom Kelly has apologised for his remarks
Tom Kelly - an official Number 10 spokesman - has apologised unreservedly for comparing Dr Kelly to the fictional character Walter Mitty.
He said the comments came in what he thought was a private conversation.
Discussions between journalists, politicians and officials in Westminster come in a number of forms.
There is the straightforward, on-the-record comment, fully attributable to the speaker.
Then there is off-the-record, a hazier area which to a degree depends on the relationship between the two sides.
A politician or civil servant may speak to a journalist off-the-record knowing - and hoping - his or her comments will be used but attributed not to themselves, but to "sources".
Then there is the "background" chat - an off-the-record conversation not intended for publication.
In some cases, the arrangement is clear - the discussion is not for quoting, but to give a journalist a wider understand of the issue in question.
But some journalists also feel that no-one can really expect to tell them something without the possibility that it will appear in print or on the airwaves.
Which is why such discussions depend to a great extent on the relationship between the journalist and his or her source.
So why would a government spokesman like Tom Kelly risk a conversation with a journalist with the intention that the content is not for publication?
The simple answer is that it helps both sides to be able to talk off-the-record.
It creates an environment where points can be clarified.
And some officials may use such non-attributable conversations as an opportunity to try to get a reporter to take a particular line when they write their story.
It is therefore a daily occurrence for journalists to ask to step momentarily behind the official line and hear what people close to the centre of power really think is going on.
Even Downing Street briefings for political journalists were on "lobby terms" - off-the-record - during Margaret Thatcher's day, with the prime minister's press secretary referred to as "government sources".
It was a similar story under her Tory successor, John Major, who appointed career civil servants as his press secretaries - though the arrangement did start to move closer to on-the-record briefings.
But the method of unattributed briefing really only ended when Tony Blair came to power, with meetings between journalists and Alastair Campbell sourced to the prime minister's spokesman.
Guardian political editor Michael White told the BBC that putting such briefings on-the-record was aimed at avoiding the kind of confusion created over Tom Kelly's comments.
But he added: "We all have conversations in the margin - sometimes physically as you leave the building, sometimes you ring people up for another chat and chew the fat and then you get into grey areas.
"I think on balance if Tom Kelly, had I rung him and had a chat discussing the options, why did Dr Kelly need to do this dreadful thing, hypotheses were being tossed around and Mr Kelly said what happened, I wouldn't have used a lethal phrase like (Walter Mitty) and nor would he have expected me to."
But the former spokesman for Margaret Thatcher, Bernard Ingham, said his assumption had always been that his remarks would be sourced if he said anything newsworthy.
"Whenever I spoke to journalists I always assumed even if I was speaking on lobby terms - i.e. not for attribution - I would be attributed if in fact I said anything remotely sexy," he told BBC Radio 4's Today programme.
It gets even more complicated when politicians or their spin doctors brief against rivals from their own political stable.
This often happens when senior people within government - normally not civil servants - are concerned by something another senior individual has said or done.
The former Northern Ireland secretary Mo Mowlam was convinced that she had been undermined by people briefing she was not up to her job.
All such briefings would have been given on a strictly non-attributable off-the-record basis.