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November

 * On 23 November, the Doctor (possibly in his seventh incarnation) battled Lady Peinforte with the help of Roundheads, then launched the Nemesis from a meadow in Windsor. The Doctor calculated the statue would pass Earth every twenty-five years before returning in 1988, then set his watch to remind himself. (DW: Silver Nemesis)

Dates unknown

 * Some time after her initial defeat by the Doctor, Lady Peinforte hired a mathematician to calculate when the Nemesis would return to Earth. Once a date of 23 November 1988 had been calculated, she and her henchman Richard Maynarde killed the mathematician and used his blood in a black magic ritual to transport themselves to 1988, with the help of a time storm created by Fenric. (DW: Silver Nemesis, The Curse of Fenric)