When first conceived he was imagined to be a traditional stereotype of middle-aged gentleman novelist, an academic dressed in tweed and smoking a pipe.
When the actor Peter Wyngarde was cast in the role he added his creative input to the character and persuaded Berman and Spooner to do something much more contemporary.
[1] The ITC publicity material for the Department S series says; Jason King is a novelist – a successful writer of crime thrillers, with a vivid imagination and flamboyant personality.
He always sported a signature 'Jason King' droopy moustache, hair that looked like a bearskin hat and a wardrobe mostly of wide-lapelled, three-piece suits, cravats, kipper ties and open-necked shirts in colours from infra red to ultra violet.
Jason King drives a Bentley S2 Continental Sports Saloon with Swiss number plates BE20838.
He has no family to speak of but in the Department S episode "A Fish Out of Water" it is revealed that he is a widower whose wife, Marion King (a film actress), was killed in a plane crash.
In the episode, Jason meets a character named Michelle Duplay who reminds him of his late wife.