This agency was founded back in the dark days of the Neualtenberg War, when Caledon's military and intelligence agents were far afield. The Guvnah, in his wisdom, created a central office for coordination and intelligence gathering. This was essential to the war efforts then, and to the growing Independent State now.
Her Grace, Eva Bellambi is the head of MI-5. There are both foreign and domestic field agents, and clerks employed therein. Several of the known agents of MI-5 are Amplebeak Tinlegs, Diamanda Gustafson, Hotspur O'Toole, and Lady Kate Nicholas. State security requires that most MI-5 activities are classified and may not be known to the general public.