Nafeez Ahmed comments further:
http://nafeez.blogspot.com/2007/05/inside-crevice-77-and-security-debacle.html

From the article:

Why was an assessment that Khan needed to be prioritized, by officers on the ground monitoring him, rejected by senior officers? Did it have something to do with the possibility, mentioned by Charles Shoebridge, a 12-year veteran Metropolitan Police detective and Royal Military Academy graduate, who told BBC Newshour (June 2006):

``The fact that that has been so consistently overlooked it would appear by the security service MI5, to me suggests really only one of two options. Either, a) we've got a level of incompetence that would be unusual even for the security services. But b) possibly, and this is a possibility, that this man Khan may even have been working as an informant for the security service. It is difficult otherwise to see how it can be that they've so covered his tracks in the interim.''

The Antagonist also comments (interesting):
http://antagonise.blogspot.com/2007/05/mrs-mohammad-siddique-khans-fall-from.html