A cynical, dedicated and, initially, mistrusted agent of the Space Security Service in the far future. He had reached second rank by the time he became involved in the conspiracy between the Daleks, Mavic Chen-the guardian of the Solar System and Vyon's superior, Karlton. Eventually convinced of Chen's betrayal, Vyon joined forces with the Doctor, Katarina and Steven Taylor, traveling to the planets Kembel and Desperus before returning to Earth. Unfortunately Chen had ensured that Vyon was painted as a traitor and before he could explain, Vyon was shot dead by a fellow SSS agent Sara Kingdom, his sister.