Henry Cavill to play new Sherlock opposite Millie Bobby Brown in 'Enola Holmes'

Henry Cavill is to trade his cape for a deerstalker, taking on the role of Sir Arthur Conan Doyle's iconic sleuth Sherlock Holmes.

But there's a twist – he'll be second fiddle to Stranger Things star Millie Bobby Brown playing the much younger sister to Sherlock and Mycroft Holmes, Enola.

The movie will be based on Nancy Springer's Enola Holmes books, in which the young detective proves herself just as capable as her elder siblings.

Helena Bonham Carter has also been cast as Enola's mother, while Harry Bradbeer, who directed both seasons of Fleabag as well as episodes of Killing Eve, will be behind the camera.

Brown, who is still only 15, will also produce the project, via her company PCMA Productions.

Legendary Pictures will make the movie, having cast Brown in the most recent Godzilla movie, Godzilla: King of the Monsters.

In the books, Enola Holmes is the 14-year-old sister of Sherlock, who is 20 years her senior.

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There are six books in all, this first being 2006's The Case of the Missing Marquess, making this a potential franchise opportunity, if things go well at the box office.

Cavill, meanwhile, is next up in The Witcher for Netflix, playing the titular monster hunter from Andrzej Sapkowski's book series.

The appeal of Sherlock Holmes continues to endure, and the super sleuth is estimated to be the most prolific screen character in the history of cinema.

In recent years he’s been played on the small screen by Benedict Cumberbatch in BBC One’s Sherlock, and Jonny Lee Miller in CBS’s Elementary. On the big screen we’ve had versions starring Robert Downey Jr. (Sherlock 3 is coming soon), Sir Ian McKellen in Mr. Holmes, and Will Ferrell in Holmes and Watson.