Tina Drake

 was a 51st century Time Agent who was sent to investigate a temporal anomaly caused by the Fifth and Tenth Doctors. She first travelled back to 1809, where she met the Fifth Doctor in the catacombs of Paris. She was informed by the Doctor that her pseudonym translated to "grapefruit" and did not refer to a place in the Dordogne. Discovering Cybermen, she escaped via vortex manipulator while the Doctor was frozen in stasis until 1922. She couldn't follow the Doctor to the future, so went back to her home time to do some more investigation before rejoining him and his later incarnation in the 18th century. She accompanied both the Doctors to find out when the Cybermen first contacted Joseph Delon. (AUDIO: The Gates of Hell)