(written from a Production point of view)
John Kingsbridge was the pen name of writer John T. Dugan (11 October 1920 – 24 December 1994; age 74). He wrote the Star Trek: The Original Series second season episode "Return to Tomorrow". In 1968 he earned a Writers Guild of America Award nomination for his Star Trek contribution.
Dugan chose to be credited under his Kingsbridge pseudonym, because he was dissatisfied with Gene Roddenberry's rewrite on his script. Roddenberry's version had Sargon and Thalassa fading away into oblivion at the end of the episode, which went against Dugan's Catholic beliefs. (These Are the Voyages: TOS Season Two)
Dugan, again writing as Kingsbridge, went on to co-write an episode of the NBC television series Mission: Impossible entitled "The Vault" along with "The Tholian Web" co-writer Judy Burns. Also writing as Kingsbridge, he co-wrote the 1969 film Shark! and served as a writer on Adam-12 and Doc Elliot.