John „Jack” Robinson jest jedną z głównych postaci dwóch książek, jak i serialu telewizyjnego Miss Fisher's Murder Mysteries. Wcielił się w nim australijski ak tor Nathan Page.
As a child Jack inherited a coin collection from his uncle Ted. He was interested enough in it that Hugh knew him as a coin collector, even though he sold his collection at age twelve.
Jack Robinson is a very methodical, rational man who would prefer to operate within the rules. Miss Fisher constantly challenges him, and unerringly delivers results through unconventional methods.Jack is reluctant to work with Miss Fisher but is unable to ignore the veracity of her information. He begins to allow her as a collaborator but still within boundaries. He has feelings for Miss Fisher but his ex-wife Rosie is a complication in the situation as she still has feelings for him.
Physically he is a man by the well-shaped body, tall and with a clear skin. He has brown hair and blue eyes. Because of his work always dresses in suits, is very elegant and well-mannered but can be extremely persuasive and sometimes violent when the occasion demands.
Jack is fluent in German but lacks confidence in his French. He knows how to play the piano, and has a bass-baritone singing voice.
Jack is a talented, capable, "by the book" detective with a calm and practical disposition. He rarely loses his composure or displays emotional outbursts, a foil to the more passionate Ms. Fisher. As a detective, he sees himself as a servant of the law, and that it is the duty and obligation to follow it impartially to wherever, or whoever it leads to regardless of personal feelings, or possible retaliation from those in power. In "Queen of Flowers" he arrests the mayor without hesitation after his predatory abuse of young girls is brought to light.. He follows facts and evidence per procedure, but will always accept new evidence if it is presented to him . This rigidity is not out of pride or snobbery, but out his duty to protect the citizens he serves. He has shown a willingness to bend the rules slightly if it serves to ensure proper justice is served. Often allowing, or even encourage Phryne to pursue leads in less than legal matters, knowing that she has the flexibility to find information in a less than legal manner that he does not. He gives Phyrne incriminating pictures of two homosexuals to destroy since he "as a servant of the law" he cannot.
His outwardly stern and conservative appearance hides an open-minded, accepting and even humorous personality. His main reason for dismissing Phryne early on is based less on her being a woman, and more because she is a reckless and impulsive private citizen with no training, who could likely compromise an investigation or get herself hurt.
However, Phryne shows that she is a highly capable private detective who can take care of herself, the readily accepts her help and is even shown to display a large amount of trust in her.
He has also shown to accept and endorse the growing trend of women's independence and right to equality and has even gone to bat for Phryne when she is dismissed or talked down to other law enforcement individuals because she is a woman.
Phryne and Jack share a mutual respect for each other, and, while polar opposites tend to bring out the best in each other when solving crimes. Jack's stable, practical nature brings Ms. Fisher "back down to earth" so to speak. Phryne's emotional, gut instinct encourages Jack to look past the logical evidence which will bring out the true perpetrator.
Jack recognizes that Phryne is a capable detective and valuable resource, holding a large amount of trust and respect for her. If she tells Jack something is amiss he will take her word for it. He has a solid friendship with her, often joining her for a drink, dinner or chat.
Phryne and Jack's "will they? won't they?" relationship is a key part of the series. They frequently engage in witty, flirtatious banter, seemingly acknowledging that while they share an attraction, they have no desire to engage in anything more. However, as the series continues it becomes clear that their attraction and feelings become much deeper and stronger. He displays a rare emotional reaction when it appears that Phryne has been killed in a car accident, and even distances himself from her, as a result, feeling she is emotionally compromising him.
By the third season Jack was a regular customer at Strano's Italian restaurant, where he was on very good terms with Concetta Fabrizi, a member of the family who owned and operated it. She called him Gianni.
Jack: Make a note that nothing seems to be missing from the crate. Looks like they were interrupted.
Jack: Oh, and did you make a note about leaving the scene of the crime in order to escort Miss Fisher home?
Hugh: She made a request, sir.
Jack: Miss Fisher is going to make a good deal of requests, Constable, and, while there may be circumstances in which we can be of mutual benefit to each other, we need to establish right up front who wears the trousers in this arrangement.
Phryne: What evidence do you have that it was me who broke into the book shop?
Jack: An Hispano-Suiza parked outside at the time.
Phryne: rolling her eyes If a tree falls in a forest...
Jack: ...you were very likely somewhere close by wielding the axe.
Phryne: I didn't pick you as a Gilbert and Sullivan fan, Inspector.
Jack: Constable Collins neglected to mention the tickets were for an operetta.
Phryne: A pleasant surprise, then.
Jack: One for which he will most definitely pay the price.
Rosie: I accused you once of a lack of ambition. I wanted you to climb the ladder like Father. But I can see what you like about where you are. laughs You're a different man these days, Jack. You've got your fight back.
Jack: Probably just that lack of ambition.
Rosie: Or escaping a marriage that didn't suit you.
Jack: It's war what didn't suit me.
Phryne: So you don't think it was a coincidence either.
Jack: In my experience there's no such thing.
Phryne: Remind me to bring you on my next break-in. You're really quite useful.
Concetta: happy to see Jack Gianni! Ciao!
Jack: Concetta. Va bene.
Concetta: So early tonight! But, your table is always waiting.
Concetta: Let me take your coat.
Concetta pours wine for Jack and smiles at him.
Concetta: See? I know what you like.