The titles used by Mackintosh are actually based on those of the CIA:
Directorate of Operations
Directorate of Intelligence
Directorate of Administrative Services,
although in the CIA the officers are Deputy Directors (the Agency is run
by a DCI, Director Central Intelligence); DD/Ops, DD/Int and DD/AS.
Other elements of SB are CIA-oriented: the Covert Action Staff (SPA
equiv.) is under DD/Ops, as is Counter-Intelligence (security is under
DD/AS).
In fact, the Directorate of Intelligence (CIA) and Requirements
Directorate (SIS) are very different creatures; Intelligence performs
"all source analysis" (agents + SIGINT + satellite + open sources [press
&c]) for the Whitehouse, much as the JIC does for Cabinet here.
Requirements Directorate at SIS handles liaison between SIS and its
Whitehall consumers who actually perform their own all-source analysis.
The description of D/Int's work in SB appears closer to DD/Int in the CIA
than DR in SIS.
Where am I leading? Mackintosh seems to have cannibalised CIA
organisation for the SIS in his series. To my knowledge there is in fact
one book which outlines SIS structure on the basis of a direct comparison
with the CIA, and refers to a "small section which handles paramilitary
operations" -- Harry Howe Ransom, _The Intelligence Establishment_
(1971). I would put money on Mackintosh having used this as a source, if
he wasn't ever actually R3.
By the way, I'm not that worried about ending up face down in a canal
working on the thesis.
That sort of thing doesn't really