Philip Garret was the identity assumed by the deep-cover Cythosi agent Skuarte on Coralee. He helped start the colony to help grow the incubating Krill hidden on the planet.
By the time the Seventh Doctor visited, Garret had been undercover for twenty years and was suffering an identity crisis. He was unsure whether he was Garret, Skuarte or the Treeka'dwra, a Coralee deity. (PROSE: Storm Harvest)