Tanya (The Sound of Drums)

Not to be confused with Tanya Lernov

Tanya was a woman who was on board the Valiant at the time of The Master's assasination of President Winters and then worked on board during "the year that never was"

Biography
Tanya was on board the Valiant when The Master, posing as the British Prime Minister under the alias of Harold Saxon, ordered the assasination of then President of the United States Arthur Coleman Winters by the Toclafane. She witnessed the Toclafane's invasion of Earth and through the next year was forced to work for the Master on board the Valiant. (DW: The Sound of Drums)

When Jack Harkness destroyed the Master's Paradox machine, events went back to the moment after the President had been killed. Though all the people on the planet below forgot about the events of the past year, Tanya (along with everyone else on board the Vailiant) remembered due to the aircraft carrier's position at the "eye of the storm" (as the paradox machine was on board). (DW: The Last of the Time Lords)