Turlough and Gibbs once climbed the wall of the girls' school. When the girls saw them, their screams were so loud that Gibbs fell back over the wall and fractured his collarbone. (AUDIO: The Memory Bank)
Like Turlough, Gibbs was from Trion. However, his family supported the faction hostile to that supported by Turlough's family in the Trion Civil War. Turlough was unaware of Gibbs' unearthly origin until they met again in 2013.
Gibbs met Turlough in The Pescadorian. He marvelled at his schoolmate's failure to age, joking that he must have a "a portrait in the attic". By this time, Gibbs was under the influence of Mulkris. He was assigned to retrieve the Watcher, an eye of Eldrad, which he bought from Rocco. He intended to use Turlough, whom he brought under Mulkris' influence, as a carrier for the eye. However, after looking at the Watcher, Gibbs became loyal to Eldrad, deciding that the scientist must live, not die. The eye leaped from its storage contained and implanted itself in Gibbs' forehead.
The Fifth Doctor took Gibbs to Kastria where he used the Doctor's TARDIS to restore Eldrad, who took his likeness. This Eldrad was killed by an existing one using a dart of acid. (AUDIO: Eldrad Must Die!)