Reports emerged last year (18) suggesting Cumberbatch was at the top of studio bosses' list to feature in a "Spamalot" movie, starring as King Arthur, with "Game of Thrones" star Peter Dinklage wanted as his trusty sidekick, Patsy, and funnywoman Tiffany Haddish as the Lady of the Lake.
However, Eric Idle, one of the original members of the classic British comedy troupe, who is writing the film's script, reveals Benedict was unable to commit to the project.
Idle was quizzed for an update on the "Spamalot" film by a Twitter follower, who asked, "Are you really making 'Spamalot' the Movie? Like, with real singing? And, Benedict Cumberbatch and Tiffany Haddish too...?"
"Sadly not Benedict who has to put on tights or something. You know those types of movie (sic)...," Idle replied, hinting at Cumberbatch's superhero role as Doctor Strange. "he was very nice about it. We'll announce the cast when it's done."
The "Spamalot" stage musical, which is based on the 1975 film "Monty Python and the Holy Grail", debuted on Broadway with Mike Nichols as director in 2005, and it became a smash hit, earning 14 Tony Award nominations, and winning three, including Best Musical.
Apart from Idle's comments on Twitter, no further details about the planned film version have been released, except for the fact that theatre director Casey Nicholaw, who worked as a choreographer on Broadway's "Spamalot", will take charge of the movie.
It had originally been expected to begin production in early 2019, although it's not clear if that timeline is still in place.
Meanwhile, Cumberbatch has signed on to reprise his role as Doctor Strange for a sequel to the 2016 movie of the same name, while he has also featured as the powerful sorcerer in "Thor: Ragnarok", and "Avengers: Infinity War".