There is very good reason to believe that that letter was a fake – and a significant one because there is equally good reason to believe that it was one product among many from a new machinery of propaganda which has been created by the United States and its allies since the terrorist attacks of September 2001.

For the first time in human history, there is a concerted strategy to manipulate global perception. And the mass media are operating as its compliant assistants, failing both to resist it and to expose it.

The sheer ease with which this machinery has been able to do its work reflects a creeping structural weakness which now afflicts the production of our news. I've spent the last two years researching a book about falsehood, distortion and propaganda in the global media.

The "Zarqawi letter" which made it on to the front page of The New York Times in February 2004 was one of a sequence of highly suspect documents which were said to have been written either by or to Zarqawi and which were fed into news media.

This material is being generated, in part, by intelligence agencies who continue to work without effective oversight; and also by a new and essentially benign structure of "strategic communications" which was originally designed by doves in the Pentagon and Nato who wanted to use subtle and non-violent tactics to deal with Islamist terrorism but whose efforts are poorly regulated and badly supervised with the result that some of its practitioners are breaking loose and engaging in the black arts of propaganda.