Therefore, its known narrative elements are not a part of the Doctor Who universe as we, on this Wiki, choose to define it. It may have been the basis for a similar story in another medium, however — and that story may indeed be valid.
The Terror Flash of Cygnus was a story originally intended to be published for the Doctor Who Annual 1967 but was rejected by the show's story editor Donald Tosh after having read it. In a letter from the Editorial Assistant of Publicity to the publications executive, Tosh described the story as "abominably written" and noted that its details of the Doctor and how the TARDIS worked was inaccurate. They believed that any fans of the show would find the story confusing, and that it was "below any standard that we would find acceptable."