In The Show
Gregory first appears in Episode 1 attending the officer's meeting about the situation of Erebus. He tells Sir John that Erebus could still go a few knots with the boilers going at full power. At the end of the episode, Sir John tells Lieutenant Henry Le Vescontre to inform Mr. Gregory to start drawing down Erebus' steam engine for the winter months. In the beginning of episode 2 he informs Sir John and Commander Fitzjames regarding the state of the steam engine and how he can get it running within a day if leads are found. He later appears briefly in episode 5 where tells Lieutenant Edward Little that men have been leaving small trinkets behind for Lady Silence out of superstition and that Fitzjames orders them removed every morning and promises punishment for leaving them. Gregory does not appear to be part of the group that abandoned both ships in 1848 so it is most likely he died in carnivale fire.
- In 2021, DNA analysis was done on a set of skeletal remains found on King William Island in the 1990s and they were confirmed to belong to John Gregory.