The Minister of Chance's female assistant

A female assistant was a travelling companion of the Time Lord known as the Minister of Chance. She accompanied him to the planet Alnelan in the interim of General Tannis' attempt to release a plague there, something that the Minister had travelled to the planet specifically to prevent with the aid of the Seventh Doctor. She is later said to have "wandered off" somewhere. (NOTVALID: Death Comes to Time)