Martin Freeman and Isla Gie to appear in Flavia de Luce

Martin Freeman and Isla Gie are to star in 'Flavia de Luce'.

The pair have joined the cast of the big screen adaptation of Alan Bradley's bestselling novel 'The Sweetness at the Bottom of the Pie: A Flavia de Luce Mystery'.

According to Variety, Protagonist Pictures will look for international buyers at the Cannes film market.

Bharat Nalluri will direct the motion picture, and it will be produced by Paula Mazur and Mitchell Kaplan.

The novel tells the story of 11-year-old Flavia (Gie) who turns detective when her father is accused of murder after she discovers a dead body in her family home.

Protagonist Pictures CEO Dave Bishop and chief commercial officer George Hamilton will be executive producers on the project.

Bishop said: "Flavia is a most charming and resourceful heroine with an insatiable curiosity in her fearless pursuit of the truth and we have no doubt this amateur detective will become a firm family favourite as she jumps from page to screen.

"Full of mystery, suspense and humour and rounded out with a fantastic cast, this is exactly the type of film audiences are craving for and we are honoured to be launching Flavia’s first big screen adventure into the marketplace."

Freeman is also starring in forthcoming film 'Miller's Girl' alongside Jenna Ortega.

While plot details are being kept under wraps, the story will follow a creative writing assignment which leads to complex results for a teacher and his talented student.

Freeman is expected to take on the role of Jonathan Miller in the movie, and while it has not been confirmed who Ortega is portraying, she is expected to be cast as the student.