Helena Bonham Carter is set to join Millie Bobby Brown in a new Sherlock Holmes film franchise.

Helena Bonham Carter

Helena Bonham Carter

The 53-year-old actress is set to star alongside the 'Stranger Things' star in a host of movies based on Nancy Springer's young adult fiction book series 'The Enola Holmes Mysteries' with Harry Bradbeer at the helm.

'The Enola Holmes Mysteries' tells the story of the titular younger sister of Sherlock and Mycroft Holmes who is also a detective and, according to The Hollywood Reporter, Carter will play Enola's mother and Jack Thorne has penned the script for the new film.

There are a total of six novels in the series, 'The Case of the Missing Marquess', 'The Case of the Left-Handed Lady', 'The Case of the Bizarre Bouquets', 'The Case of the Peculiar Pink Fan', 'The Case of the Cryptic Crinoline' and 'The Case of the Gypsy Goodbye'.

Brown, 13, developed a relationship with Legendary Entertainment after recently making her big screen debut as Madison Russell in 'Godzilla: King of the Monsters'.

Legendary are producing with Brown and her sister Paige Brown via the duo's PCMA Productions shingle.

Carter will next be seen playing Princess Margaret on Netflix's 'The Crown' and her role comes as the whole cast of the original two seasons have been replaced, as the show moves ahead in time to show a later time in Queen Elizabeth II's life.

Claire Foy has been replaced by Olivia Coleman in the lead role, whilst Tobias Menzies will take over from Matt Smith as Prince Philip.

And Helena recently revealed she was "terrified" about taking on the role because of the pressure to follow on from the "successful" first two series.