I recently attended a briefing by a ex-SAS Captain of long-standing, to do with civilian airline security.
As an aside he made a few comments regarding his opinion of the performance of B20 - he personally had little praise for the professional conduct of McNab, and even less regard for his decision to write books...
As for those in authority supporting McNab or otherwise - it may be that the good
PR from these books does the MOD a favour, and that by design most those in the SAS have the dignity and professionalism to keep their heads down?
I read the books many years ago - thought they were great - but have since had enough cause to doubt the integrity of the protagonist. Shame.