MI11

MI11, or Military Intelligence, Section 11, was a department of the British Directorate of [Military Intelligence (United Kingdom)|Directorate of Military Intelligence], part of the War Office.
During the Second World War, MI11 was responsible for field security: protecting British military personnel from enemy agents and "fifth columnists" amongst civilian populations, in theatres of war. As such, MI11 assumed a role formerly assigned to the Field Security Police.
Section 11 was absorbed into the Intelligence Corps after the Second World War.