Theory:Doctor Who television discontinuity and plot holes/The Christmas Invasion


 * It is left unexplained why Britain's space program has apparently reverted to celebrating unmanned probes arriving at Mars when The Ambassadors of Death established that by this time Britain had already sent manned missions to Mars.
 * There is actually a real-world example of such reversion occurring: America's NASA program sent manned missions to the Moon in the 1960s and 70s yet by the 2000s had reverted to again sending unmanned probes to the moon. The secrecy involving restricting public knowledge of alien life might also imply that those earlier missions may not have been public knowledge.
 * In The Ambassadors of Death the Time Lords were still around.The Doctor could have visited a parallel universe, as it was still possible to do so at that time.


 * After indicating to Rose how important Harriet Jones becomes to Britain and planet earth (DW: World War Three), here he proceeds to sabotage her career. What about his many spiels about his being forbidden to change history?
 * Some events can be changed, as established in The Fires of Pompeii. This must be one of them. In any case, Harriet Jones was to be vital to the world in The Stolen Earth. In that story, her death was not witnessed by the audience or any of the characters. It remains possible then, that she survived and did eventually serve the two more terms and usher in Britain's Golden Age, as predicted by the Ninth Doctor. Alternatively, it was the Doctor deposing Harriet that led to the Master to be elected in her place.


 * How is the scarf that the Fourth Doctor wore in the TARDIS wardrobe? The Fifth Doctor took it apart in his first episode, and the Ninth Doctor was noted on Clive Finch's website to throw a scarf into a skip.
 * It is possible that the Fourth Doctor had multiple scarves, just the Tenth seemed to have multiple blue suits.
 * The Doctor could have acquired a new scarf, or simply re-sewn the old one if he became nostalgic.
 * After dumping it in the skip he may have changed his mind and got it back.