With the Andy Coulson story rumbling on , there is much chat in Westminster, as well as a number of references  in print, about "Alastair Campbell's rule". This refers to a supposed dictum from the legendary former spin doctor about how long a story must remain in the headlines before its victim is finished.
In search of the original quote, I must confess to having spent several hours trying to find it on the internet to no avail, despite some modest confidence in my own Googling skills.
The consensus in the Commons press gallery seems to be 12 days, but a search including that only throws up endless links to the fact that Campbell published the latest edition of his diaries  12 days after Gordon Brown left office. There is a reference to 11 days in a column by the late Alan Watkins. On Twitter, it emerged that the Dutch seem to think it was 9:
Kan Camerons voorlichter aanblijven? Adagium Alastair Campbell: na 9 dagen voorpaginanieuws ben je onhoudbaar. We zitten halverwege dag 3.
But the truth remained elusive. Eventually, somewhat desperate, I decided to go to the horse's mouth and ask Campbell what he actually said. Here was his surprising reply:
I honestly can't remember. I wonder if I ever did? Sometimes quoted as a week, sometimes ten days, sometimes a fortnight. But I don't remember saying anything at all.
If anyone has more luck recalling it then, details below, gratefully received.