Do Dirk Gently and The Hitchhiker's Guide exist in the same universe?

Question

There are several common elements between the Dirk Gently and Hitchhiker's Guide universes which I noticed while re-listening to them in succession, but there are also differences:

1. Thor and Asgard exists in both universes

   • Thor is alluded to in The Restaurant at the End of the Universe:

     "And do we also have, do we have ... a party of minor deities from the Halls of Asgard?"
     Away to his right came a rumble of thunder. Lightning arced across the stage. A small group of hairy men with helmets sat looking very pleased with themselves, and raised their glasses to him.
     Hasbeens, he thought to himself.
     "Careful with that hammer, sir," he said.
     They did their trick with the lightning again. Max gave them a very thin lipped smile.

     And then he's flirting with Trillian at the party in Life, the Universe and Everything, and confirms that this was him that was being referred to in the previous book:

     The first thing Arthur noticed as they entered into the thick of the party [...] was Trillian being chatted up by a Thunder God.
     "Didn't I see you at Milliways?" he was saying.
     "Were you the one with the hammer?"
     "Yes. I much prefer it here. So much less reputable, so much more fraught."
     [...]
     "Have you met Thor? He makes thunder."
     "Hello," said Arthur. "I expect that must be very interesting."
     "Hi," said Thor. "It is. Have you got a drink?"
     "Er, no actually ..."
     "Then why don't you go and get one?"
     "See you later, Arthur," said Trillian.

   • Thor is also a pivotal character in The Long Dark Tea-Time of the Soul, his anger causes devastation like turning Dirk's secretary into a drinks dispenser and engaging in a fight with the RAF that turns a jet and its pilot into a giant bird.

     • The problem with this is I'm not certain they're the same Thor, as the one met at the party is very suave however Thor in Dirk Gently is a furious, fairly dim and clumsy character. This version of Thor does match the depiction of him in And Another Thing..., but as this wasn't written by Douglas Adams himself I don't really consider it evidence.

2. Sirius Cybernetics Corporation exists in both universes

   • They manufactured Marvin (and all sorts of other things) in the Hitchhiker's Guide universe.

   • They also exist as an Earth-based corporation as the newspaper salesman Dirk talks to in episode 1 of The Long Dark Tea-time of the soul mentions that Sirius Cybernetics Corp bought out WayForward Technologies (the company owned by the first victim in the previous novel, Dirk Gently's Holistic Detective Agency).

     • The problem with this is that humans obviously didn't create the Sirius Cybernetics Corporation from HHGTTG because we're just a Mostly Harmless species which never made contact with aliens until the minutes before our destruction.
       • Unless it's a different, time-travelling human society somewhere in Whole Sort of General Mish Mash

Is there anything which unambiguously demonstrates whether they are the same universe?

Answer 1

Yes, they're part of the same universe. Probably. Or maybe not. It really rather depends who you ask.

The BBC's Dirk Maggs certainly thinks that they were. And he's got Adams' original notes to back it up:

“There is definitely Hitchhiker’s/crossover,” explains Dirk Gently adapter-in-chief and director Dirk Maggs. “In this second series there is one particular idea from Douglas’s notes for the third [unfinished] Dirk Gently book which at one point he thought might be a Hitchhiker’s book. It’s a very simple idea that puts one of the Hitchhiker’s characters in the same universe as Dirk Gently in a way that I thought had enormous potential.

In this series we find that the characters in both universes are inhabiting the same world, and I think where we’re going with this is something that actually resolves later on in Hitchhiker’s. It’s turning into a bit of a prequel!”