Hathaway, like Inspector Morse, Lewis' old boss from his days as a Detective Sergeant, is cerebral. Unlike Morse, Hathaway is a Cambridge graduate, trained in Theology, and rather successful athlete, as his nickname 'Atta-way Hathaway' (revealed by a rival coach at Oxford) would attest, being a rowing star while at Cambridge. He subsequently trained for the priesthood in Oxford. In the episode "Old School Ties" we are told by an ex-schoolmate of Hathaway's that he had been Head Boy of his school and nicknamed 'W.C.' - short for 'Wolfgang Christ' - because he "didn't know whether he wanted to be Mozart or Jesus".
Hathaway is highly knowledgeable and often shows it. He joined the police after abandoning the priesthood, and sometimes expresses scepticism about religion – when Lewis states thankfully "There is a god", Hathaway replies "If I was sure of that ... I wouldn't have joined the police force" (in the episode "And the Moonbeams Kiss the Sea").
When he first appears, Hathaway is sergeant to DI Charles Knox, whom Lewis knew when Knox was a sergeant. Knox is shown taking a breathalyser test and Hathaway states to Lewis that Knox will be put on immediate suspension for it. Hathaway is later reassigned to Lewis.
In the third episode of the second series ("Life Born of Fire") his guilt at sharing the homophobic attitudes of some of his fellow trainees is revealed when he discovers that a suicide he is investigating is a former friend, Will McEwan, who broke off his friendship with him when Hathaway urged him to reject his homosexuality.
In "Life Born of Fire" he refuses to answer Lewis's direct question as to whether or not he is gay, though at the end of the episode in a conversation with Zoe Kenneth he both implies that he has had homosexual feelings and that he wants to have sexual intercourse with her (admitting that "it's been a while"). Hathaway berates Lewis for drawing a "neat dividing line" between heterosexuals who "read Loaded and eat Yorkie bars" and homosexuals who like fashion and musicals. At the end of the episode Hathaway is seen holding a copy of Loaded and a Yorkie bar. In "The Dead of Winter", Hathaway appears to become romantically involved with a woman from his early teenage years (by going out on a date and then leaving her flat the next morning) who may or may not be suspect in a murder investigation. Lewis suspends him from the investigation fearing Hathaway crossed an ethical line. At the end of the episode Hathaway turns in his badge and tries to resign from the Police. Lewis refuses his resignation, and instead tells him: "Between the two of us we make one good Inspector. I of course, am the brains".
In the first episode of series 3 there is slight reference to Hathaway's childhood. When his father is mentioned he becomes rather irritable and changes the subject rather quickly. In the first episode of series 4 it is mentioned that Hathaway's father was the groundskeeper at the estate of a lord and that Hathaway used to play with the other children who lived at the estate.
In the same episode Lewis and Hathaway deal with a difficult case involving a complex family relationship. The eventual outcome is difficult for Hathaway to digest, leading to conjecture that he may himself have some experience in the subject matter.This links back to "Life born of Fire", where John Jo a former friend of Hathaway's asserts his friend is not happy with his life. Something in Hathaway is always questioning his desires with his duties.
In the last episode of series 5 Hathaway informs Lewis that he was talent spotted for MI5 in university, this is neither confirmed or denied by the end.