Jason King is a 'Department S' investigator as well as a best-selling novelist. As a result, he approaches each case by imagining what Mark Caine, the hero of his novels, would have done in this situation. On the other hand, often the Department's real cases find their way back into King's novels (as being solved by Mark Caine). He is flamboyant and very much into fashion (or what qualified as 'fashion' in the late 60s, anyway...).
He is also a playboy with a woman in seemingly every city in Europe, and is easily distracted, or even entrapped, by pretty girls, so usually it takes Annabelle's or Stewart's interference to get him back on track or out of trouble. However, his theories (or, rather, speculations) often prove very helpful in solving the Department's cases, or as Stewart once put it, "he has a nasty habit of scoring near misses!"
