Horatio Fable is an agent with the Agency.
Apparently that name is used for either the British Department of Security Intelligence or a division inside it.
A blurb on each of the four recorded adventures we have of him invite us to: "Meet the man who deals in danger - Horatio Fable."
"He was a tall man, with heavy shoulders and arms, narrow waist and a rugged handsomeness of face" complete with a clef in a strong chin. He has "a two-inch white scar running through the right eyebrow", not to mention "the half-dozen torso scars that were a legacy of his trade". From the images shown on his four recorded adventures, we can see that he has full, lush black hair combed straight back, thick eyebrows, and enough age-lines on his forehead to show the man has seen his share of bad things and make more than a few difficult choices.