Some of us sat downstairs in Islington with Douglas Adams’s editor, the saintly and incomparable Sue Freestone, typing out chapter after chapter of Mostly Harmless and sending it upstairs via email to where Douglas sat. There would be a from his computer, followed by cries of rage and alarm and “But that’s not what bloody happens,” followed by furious adversarial typing until Douglas had dismantled and reassembled it into something he liked—or, to be accurate, hated marginally less—at which point a glum silence would fall until some of us started typing again at our end to get ready for the next and gorilla noises from upstairs.
What really perplexes some of us is that the only way Adams could be persuaded to write Mostly Harmless at all was if it could be guaranteed that he could never, ever be called upon to write another Hitchhiker book ever again, not ever. He had had enough. So some of us—let me be straight with you; what I actually mean is “I”—sat down and worked out a plot which ended in the destruction of not only this Earth but of all possible Earths, as well as all possible Zaphods, Ford Prefects, Trillians and anyone else whom Douglas hadn’t mopped up in his previous search-and-destroy forays into the Hitchhiker diegesis. It wasn’t a good plot. It was unnecessarily complicated. The dénouement rested on a bad pun. But the idea was to make any further sequel impossible. And then, just to make sure, Douglas died.
Michael Bywater (some time last year) on Hitchhiker's Guide V