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.
It was written by Robert Sloman. It was cancelled mainly due to the fact it bore too much in common with The Dalek Invasion of Earth. It was replaced by The Time Monster, while the idea of the Daleks was inserted into the opening story, then known as The Ghost Hunters, which evolved into Day of the Daleks.