While of course most intelligence work requires discretion and goes unseen, historically, uniformed duties often involved the wearing of an armband as a kind of ‘warrant’ to enable access to locations and individuals, for example during investigations and POW questioning.
In WW1 the ‘IC’ armband was worn and at the start of WW2 an ‘FSP’ armband in black on green denoting Field Security Police/Personnel was issued, example below.
Following the (re)formation of the Intelligence Corps in July 1940 the armband changed to green/grey/green as corps colours. The example shown was issued to 556 Field Security Section based in Karachi and is marked Number 11, indicating a controlled item, an FS Section comprised one officer, one warrant officer and up to ten NCOs.
After WW2, from the 1960s, the term Field Security was replaced by Counter Intelligence and the lettering on the armband changed again to ‘CI’ although rarely worn I believe.
More Intelligence Corps insignia in my album
https://www.britishbadgeforum.com/fo...hp?albumid=339
Tim