What makes Cherie Blair's reported gaffe even worse is that everyone else in Manchester has been on their best behaviour, pretending that the Cabinet rivals love each other. It is of course in their interests to unite because they all want to go on to win the next election. Lady Macbeth, as Cherie is fondly referred to in the Treasury, doesn't give a monkeys who wins the next election so long as it's not Gordon Brown - so will say what she thinks.
I first learnt of the Cherie story within minutes of Brown sitting down in the conference. I thought a strong Number 10 denial would kill it at least on the TV, but on reflection realised that even if she didn't say the Chancellor was a liar, one could imagine her saying it. More crucially though, the story ran because what she allegedly said was probably true. Brown clearly doesn't really think that it's been a privilege to have worked under Tony Blair, though for the sake of unity he had to say it.
But just how damaging has this story been? It goes without saying that the initial media reaction has been a disaster for the Chancellor. In the pubs and clubs, if people have been discussing his speech they will only have been talking about Cherie. The content of his address will have been instantly forgotten. More worrying for the Labour Party is the realisation that this sort of story will not go away until Blair goes - and he's not going for some time yet.
The fact is that every day the PM clings to power, the less likely Labour is to win the next election. Brown would not have had to come out with all that nonsense about Blair if he had already gone.
There is no way that the unity shown in Manchester this week can last in the Westminster hot-house, so we can expect plenty more Cherie-type incidents. You only had to listen to Peter Mandelson on Today to realise there are plenty of people in Cherie's ‘Anyone but Gordon' camp. The twice-disgraced former minister just couldn't bring himself to endorse the Chancellor for PM despite all his warm words.
The Blairites are biding their time, waiting for a knight in shining armour - probably Alan Johnson - to emerge and save New Labour. But they have one big problem. As David Hill, the PM's spokesman, has said privately, the party wants Brown as leader.
When Brown becomes PM, we really will have his most important speech ever - only Cherie won't be there to spoil the show.