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One key element is left unresolved in Series 2 of the BBC radio series (the Secondary Phase), originally aired in 1980.
At the end of this Phase, Zarniwoop reveals to Zaphod Beeblebrox that at some point the starship Heart of Gold has entered the pocket universe which exists within Zarniwoop's office on Ursa Minor. But it is never made clear at what point this occurs.
As none of the events which happen within the pocket universe have really happened, an element of confusion exists as to how much of Series 2 really took place, and which parts of that series didn't really occur.
It seems certain that Zaphpod's visit to the headquarters of Megadodo Publications, in episode 1 (Fit the Seventh), must have happened in reality, because he is given details there about Zarniwoop being on an inter-galactic cruise in his office: logically, Zarniwoop and the cruise must be real, as when Zaphod meets Zarniwoop in episode 6 (Fit the Twelfth) the latter admits to being on such a cruise.
Ford is present with Zaphod in episode 6, at the meeting with Zarniwoop, so Zaphod's rescue of Ford and Arthur must also have been real.
As Zaphod does not return to the starship Heart of Gold between fleeing Zarniwoop's office and arriving on the Frogstar, that incident - and hence his being plugged into the Total Perspective Vortex - must also be real events. This is logical, as these events preceed the rescue of Ford and Arthur.
So at what point do Zaphod, Ford and Arthur become unwitting guests in Zarniwoop's pocket universe?
And do they ever leave it? The Ruler of the Universe, in episode 6 (Fit the Twelfth), seems to be aware that there is some doubt as to whether the universe he rules is real or not. This occurs after the meeting with Zarniwoop, such that Series 2 ends on an ambiguous note: have they actually exited the pocket universe -- or not?
Note to interested parties: I am (reasonably) well aware that many strange occurrences occurred in the 2nd novel written by Douglas Adams, which he based (loosely) on the 2nd radio series. But that novel has a radically different plot to the original radio show. What I'm asking about is the radio show, not the impenetrable plot of the novel.
EDIT - This question is not the same as the question it supposedly duplicates, which talks mainly about the novels. But I am asking about the radio show -- there are enormous differences of plot between the second novel and the 1980 radio series it is (loosely) based on. Also, the other question only deals with when he entered the pocket universe, but my question is asking also about the point at which he got out, and, indeed, is asking whether - on the radio- he ever did get out, since the "Man in the Shack" says things in the radio episode which imply that they are still trapped in the artificial universe, after Zarniwoop has supposedly released them from it.