Mellin Kinloch-Jones was a member of the business class on a train-city on a devastated planet. His mate was Emiliege. They had a rebellious daughter.
Mellin and Emiliege met the Fifth Doctor when he appeared in their compartment pretending to be an inspector investigating recent suicides. Mellin and Emiliege explained the train-city to him.
In reality, Mellin and the entire train-city were part of an illusion that Maya had created for the Doctor and Nyssa. (PROSE: Confabula)