MI5 Defence Security Officers and Security Liaison Officers
Defence Security Officers (DSOs) were MI5 officers attached to military General Headquarters (GHQs) from the late 1930s.1
Security Liaison Officer (SLO) is a title held by some MI5 field officers, typically security representatives to a foreign or colonial government.
As of 1981-83 SLOs were supervised by the MI5 Secretariat.2
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