El fin del tiempo
Writing in his regular column in "Doctor Who Magazine" issue 416, Davies revealed that the original title for "Part One" of "The End of Time" was "The Final Days of Planet Earth", while "Part Two" was always referred to as "The End of Time". Due to the sheer scale of the story, however, it was decided that both instalments needed the same title, differentiated by part numbers, the first such instance since "Survival".