Therefore, its known narrative elements are not a part of the Doctor Who universe. It may have been the basis for a similar story in another medium, however — and that story may indeed be a part of the DWU.
Illegal Alien was an unproduced Seventh Doctor television story. It was originally planned for season 26, but was cancelled because another World War II story, The Curse of Fenric, was on the schedule. The episode was pencilled in for season 27 before the series was cancelled. The author adapted it into PROSE: Illegal Alien. (DOC: Doctor Who: Endgame)