Neil Gaiman to adapt Good Omens for TV after co-author Terry Pratchett gave posthumous permission

“Terry and I had a deal that we would only work on Good Omens things together,” he explained to a crowd at the Barbican centre, London, the Guardian reports.

“Everything that was ever written – bookmarks and tiny little things – we would always collaborate, everything was a collaboration.”

But then Gaiman discovered that Pratchett has written him a letter to be delivered after his death, entreating the fantasy author to write a TV version with his blessing.

“At that point, I think I said, ‘You bastard, yes,’” Gaiman recalled, to the apparent joy of the crowd.

Released in 1990, Good Omens tells the story of an angel and a demon (called Azriphale and Crowley) who work together to try and raise the antichrist in a balanced good/evil setting – only to realise that they’ve mixed up two children and left the devil’s offspring (called Adam) growing up in a small village in England.

Meanwhile, a couple of witch-hunters and a young woman with a map of the future are also on Adam’s trail, just as he begins to come into his earth-shaking abilities.

Previous attempts to adapt the story for screen have included a stalled 13-part production in 2011 written by Monty Python’s Terry Jones and a cinematic release starring Jonny Depp and Robin Williams, with another former Python – Terry Gilliam – attached to direct.

Despite these disappointments, an audio adaptation starring Colin Morgan, Peter Serafinowicz and Charlotte Ritchie was eventually released on Radio 4 in 2014, with Gaiman telling RadioTimes.com at the time that the project was partially so that the ailing Pratchett would “be able to enjoy this while he's still able to enjoy it.”

Gaiman and Pratchett with Good Omens radio director Dirk Maggs (centre)

Both writers also cameo-d in the drama as policemen, an experience which Gaiman described as a “very strange, sad, sweet, funny, odd moment.”

But as for the new adaptation, both Gaiman and Pratchett’s former assistant Rob Wilkins (who also appeared at the memorial) were relatively tight-lipped.

“How much are we allowed to tell them?” Gaiman asked Wilkins teasingly before he was hushed. “Are we allowed to tell them it is a six-part television series?”

However the pair did reveal that Good Omens was only the first of many new projects based on Pratchett’s work, with an upcoming film adaptation planned for 1987 novel Mort in the works from Pirates of the Carribbean scribe Terry Russio alongside a fan-funded movie based on Pratchett’s short story Troll Bridge and a fantasy police procedural series called The Watch set in the author’s Discworld universe.

Clearly, Pratchett’s many fans still have plenty to look forward to.