Tarvick was the Crown Prince of Frentos. After a republican revolt, he fled in his spaceship, Valentine. His ship was hit by warp torpedoes and he was sent back to 20th century England. With his bright pink hair, he was able to blend in with English pop stars.
He met the Fourth Doctor and Romana II and explained his predicament. At this point, several different groups of people from Frentos travelled through time to England, some to execute Tarvick, some to prevent his execution. Eventually, the Doctor brought Tarvick back to Frentos at a time when Tarvick was unknown. (PROSE: The Clanging Chimes of Doom)