Marsh was a cameraman for EarthCom's Natural History Unit, in the Interplanetary Division. He once spent eight months filming the Geluban Quess, only to find that the camera he had used was faulty and that no footage he had recorded was usable. He wanted to build a life with a woman named Anna at one point as well.
As punishment, he was sent to film the mating rituals of the Gadot on the planet Erindra, where he spent at least five months. One day, the Fourth Doctor arrived on Erindra and informed Marsh that the Gadot were long extinct. Taking pity on the man, he brought a Gadot with him in his TARDIS and allowed Marsh to film it.
Later, Marsh showed to footage to his boss, Scullup. His boss was excited by the footage of the Doctor and sent Marsh back to Erindra to get footage of the Doctor for a reality TV series, despite Marsh's protests about wanting to spend his life with Anna.
While on Erindra waiting for the Doctor, Marsh encountered another man using the TARDIS and his young, female companion. In a series of recorded diary entries, Marsh revealed a deep hatred of the Doctor, due to his role in preventing Marsh from living a life with Anna and expressed a desire to kill him. (AUDIO: Waiting for Gadot)