In the depths of a west London industrial estate, a minor theological crisis has broken out. The biblical point in question is over whether it was Adam or Eve who took the first fateful bite of the apple, thus causing the downfall of humankind. As shouts of “quick, someone fetch a bible” echo around the production studio, the confusion is swiftly and slightly embarrassedly cleared up by a flick through Genesis.

Yet, in the process of making the first radio dramatisation of Terry Pratchett and Neil Gaiman’s bizarre and cult classic novel Good Omens – a book which grapples with the antichrist, a narcissistic angel and demon duo and a prophetic witch – such issues are simply par for the course.

The adaptation of the novel for BBC Radio 4 was an ambitious undertaking and has attracted a cast including Peter Serafinowicz and Mark Heap. The task of writing and directing the project has fallen to Dirk Maggs, best known for his BBC radio production of Hitchhiker’s Guide to the Galaxy.

“Good Omens is an epic,” said Maggs. “I go on and on about radio being the true visual medium, and I truly believe it is – it paints pictures in the imagination and bypasses the optic nerve and sneaks in through the side door. So for me, radio is the perfect medium for Good Omens. We can create everything from the armies of heaven and hell to a bunch of children playing in a chalk quarry, it’s got all those elements.”

Despite numerous rumours of film and TV adaptations, this is the first time that Good Omens has been dramatised in any format and the six-part radio drama will run every night at 11pm this week from Monday, ending in an hour-long finale on Saturday 27 December.

Maggs said the adaptation had remained very loyal to the original novel and Gaiman and Pratchett willingly offered their input on both the script and casting. The pair even make a cameo appearance in one episode, playing two policeman. Other Radio 4 stalwarts also crop up in the drama, including the panel of Gardeners’ Question Time.

“What’s really great is that both Neil and Terry have been involved in the process,” Maggs added. “I can talk to Neil about it and Terry too, for all his troubles, has fed in all sorts of ideas. Neil came to the read-through and his body language was great – if he’d stiffen slightly I’d check what word he stiffened on and possibly change it. What’s wonderful about working with Neil and Terry is they still love this book as much as the readers love it.”

Published in 1990, Good Omens was developed after Gaiman sent an unfinished manuscript, titled William the Antichrist, to Pratchett and the fantasy author liked the quirky book so much he asked to come on board and co-write it with Gaiman.

Good Omens tells the story of angel Aziraphale, who is also a second-hand book dealer and demon Crowley, who was once the serpent that tempted Eve in the garden of Eden, and their attempts to stop the coming of the apocalypse and preserve their now comfortable lives on earth.

The unlikely fictional duo are played by Heap and Serafinowicz. During the recording of one scene, which sees the angel-demon double act driving down Oxford Street at 90 miles an hour as they plot to kidnap the antichrist, Maggs turned to his producer Heather Larmour noting: “Mark’s got this holy cadence going – I think it’s because his dad’s a Methodist minister.”

Heap admitted he had been slightly intimidated taking on the character of Aziraphale and going against or ruining the vision of the angel held in so many readers’ imaginations. “It’s a fab project isn’t it – so British in that lovely dry, silly sense of humour” said Heap. “I’m very lucky to be here, let alone employed at all in this harsh world of ours. But playing Aziraphale is daunting because you suddenly become aware how widely owned books like this are on people’s minds. They have such a strong sense of this character that you are pathetically trying to portray in your own way, so I have to shut the voices out of my head otherwise I get too paranoid about whether my interpretation will go down alright.”

Discussing his double act with Serafinowicz, Heap said their opposing tonal qualities complemented each other.

“Peter does that dark thing very well and I do the slightly screechy, more pedantic character so it’s a good match” he said. “I do often end up playing pedantic, precise people but I don’t mind that I suppose.”

Maggs also praised Serafinowicz’s quick-witted adlibbing as demon Crowley, and said he would incorporate the unscripted lines and jokes into the final edit.

But Serafinowicz played down his own comedic input. “It’s a story and you can’t do anything to change that but there are bits that you can make your own, a little bit, but it’s a very small percentage really,” he said.

“This character, well he’s amazing – he’s this evil emissary of Satan but he’s not really that bad.” Serafinwicz added. “Mark and I are a double act the whole way through – we’ve known each other for years and he’s just brilliant. I love when we are in the studio, it’s really good fun and when we get into the studio put our headphones on and start recording, it’s like we exist in another dimension.”

Good Omens, BBC Radio 4, begins Mon 22 December at 11pm