Jeff Cass is an agent with MI-6.
When we initially meet him in the first of three recorded adventures, Cass is really a British adventurer living in South Africa who gets involved in the cloak and dagger world when his friend is murdered and Cass takes exception to that, poking his nose in areas several people did not want it. One of those was MI-6 who decided that since he was determined to go where he was not wanted, he might as well be useful.
Seeing how well he did and always in the need for qualified agents, the head of the organization, a man known only as 'A' having replaced some time back the previous boss, Cummings or 'C', offered him a job. 'A' was not surprised at all when Cass readily agreed. His six months at the training facility in the "West Country" resulted in extremely high marks and an overall rating of 'outstanding'. Normally the department would have started him out as a junior agent working as an assistant but 'A' chose to promote him into the top rung, the esteemed and elite 'Treble' ranks. Cass would be given the designation of 'Treble Three'.
Cass would go on to prove himself a very capable agent who got the job done quickly and efficiently. 'A' would gain an appreciation of the man's talents though he would on more than one occasion wish that perhaps Cass be a bit more "aggressive" in his dealings with the other side, a particularly harsh sentiment since Cass could not truly be considered as going easy on anyone. It struck me that 'A' was a "shoot him again just to be sure" sort of fellow while Cass was a "enough is enough" gentleman.
As far as the opposite sex is concerned, there are more than enough to keep Cass occupied and Cass shows that he is more than capable in that field as well. He does not exactly go out of his way to pursue them which is likely why they feel it necessary to come after him. He does not push them away, though.
In the scant description we have of the operative, Cass "was around six feet in height with lean, handsome features, and fair hair. His eyes were of dark blue".