LIZAND RICH IS RIGHT
Elsewhere on this message board LIZANDRICH says that this film forms a sort of trilogy along with THE FOURTH PROTOCOL and THE WHISLTEBLOWER.
They are all good films.
Politically DEFENCE OF THE REALM was loved by GUARDIAN readers like me,THE FOURTH PROTOCOL was more for COLD WARRIORS (but I loved it)and THE WHISTLEBLOWER seemed to hit all targets,the upper class elite,traitors,the indifference of ordinary people.
Knowing what we now know,that CND was backed by the Soviet Bloc (although to be fair a lot of the membership did not know this)the Americans had an end of the world view of events at the time and MI5/6 and GCHQ did have traitors in their ranks I can almost forgive the actions of the government in the film in trying to defend the realm.