Jane Tranter, executive producer of His Dark Materials, is diplomatic about that previous version. Her Welsh company, Bad Wolf, is co-producing the series with New Line for whom this is a first venture into British television. HBO is the international distributor.

She has been a Pullman fan from the beginning when she longed to do a television adaptation of the books but the rights had already gone to New Line. “So I went into my shell,” she says at a London press conference. “Then I saw the film and … I came out of my shell. I’m a believer in timing. If I’d made it then, it would have been a teatime series. I had to wait for television to go epic.”

Epic, in this particular context, means Game of Thrones , HBO’s last alternate-world mega-success. “We benefited from Game of Thrones,” agrees Tranter. “We’re grateful rather than in their shadow.”

What she relishes is what the 2007 film could not offer: “the real estate” offered by current television, which means that eight one-hour episodes can be devoted to the first book.

Judging by the first episode, however, McAvoy’s ability to flash and glitter “with savage laughter”, as Pullman puts it, conveys Asriel’s obsession and his questionable morality. Five minutes in, an apparently decent man – Clarke Peters from US crime drama The Wire, playing the master of a fictitious Oxford college – is trying to murder him. This world’s road to heaven, or hell, is peopled with ambivalent characters.

Similarly Ruth Wilson, a charismatic psychopath in British crime drama Luther, is Mrs Coulter who, once encountered on the page, is not easily scrubbed from mind or nostrils (Pullman describes her as having the hot, metallic scent of glamour). Children come to her willingly: her power is entrancing and appalling. “I hadn’t read the books,” says Wilson. “But my agent said she’s the all-time great literary villain.”

What Wilson also discovered was Pullman’s concept of the daemon: an animal companion, usually of the opposite sex, as indivisible as one’s soul.

Mrs Coulter’s is a golden monkey with whom, unusually, she never speaks. Lord Asriel’s daemon is a snow leopard. “It could have been dodgy puppets at teatime,” McAvoy remarks, with a grin. “But I can’t believe the work these guys created to complement the unity between actors and their daemons.”

That was achieved by human puppeteers, who made it easier for the actors to emote with their other halves; these were then edited out and replaced by CGI.

A further complication is that adult daemons are fixed but children’s shape-shift until adolescence. Lyra, the 12-year-old around whom the entire plot pivots, has a daemon that manifests itself as a moth, a mouse and a pine marten.

Lyra is played by British-Spanish actress Dafne Keen. In Logan , she was the child created from Wolverine’s DNA so she has form dealing with the creature within. Lyra is variously described as “a barbarian”, “like a half-wild cat” and “a coarse and greedy little savage”. She’s also blonde, which Keen isn’t. (Spoiler alert: this surely had some bearing on the appearance of at least one other actor.)

“Personality-wise, we’re not far off,” Keen tells the invited audience at the screening. “Very, very noisy and quite cheeky.” And, like Lyra, the weight of worlds is resting on her shoulders.

Unusually, filming is already halfway through the second season (based on Pullman’s second book in the series, The Subtle Knife) because Keen, now 14, is growing up and herself shape-shifting. Afterwards, there will be a pause while the production considers “the magnificent beast”, as Tranter puts it, of the third book, The Amber Spyglass.

Whether that happens, of course, will depend on this universe’s reaction. The first episode, with its zeppelins, ancient colleges, references to unusual peoples (gobblers, “gyptians”) and glints of fascism beautifully blends the familiar and the strange. As readers know, to succeed it must become even stranger and increasingly dark. “You don’t work with BBC and HBO and do a vanilla adaptation,” promises Tranter.

Jack Thorne, who wrote Harry Potter and the Cursed Child for the stage, did the screenplay. Persistence is evidently one of his many talents: he worked on 46 drafts for the first episode. (Asked what his daemon would be, he immediately replies: “A woodpecker.”)

“I do think the books are perfect,” he says. “And when you’re given perfection, that’s scary as s***.”

Thorne had the advantage of being able to flesh out events using materials, dark and light, from later books. The opening sequence, as fans will recognise, is actually taken from La Belle Sauvage, a prequel to Northern Lights written in 2017.

Whatever the public thinks, the prime creator himself is thrilled. At the screening, Pullman gives the series his gleeful approval: “I could not be more delighted with the result!”

As it happens, the series was filmed in Wales where as a schoolboy he first heard Milton’s Paradise Lost read aloud. “I remember my hair standing up, my skin bristling,” he says. Now, in what Thorne calls these “scary times”, the power of words and imagination head out to do battle with the voice of authority.

The first episode of His Dark Materials will be broadcast on HBO on November 4