Terry Pratchett's Wee Free Men film in development

Fantasy author Sir Terry Pratchett died last year

A film based on Sir Terry Pratchett's comic fantasy The Wee Free Men is being developed by The Jim Henson Company.

The book tells of a young witch's adventures with the NacMac Feegles, a fierce clan of kilted sheep-stealing, sword-wielding, six-inch-high blue men.

The characters are known as "pictsies", a name based on the Picts, tribes that were dominant in Dark Age Scotland.

Sir Terry's daughter Rhianna Pratchett is adapting the novel for the feature film.

She is an award-winning scriptwriter for videogames, comics, film and TV - and won the Women in Games Hall of Fame award in 2013.

The Wee Free Men form part of Pratchett's Discworld

The Wee Free Men was the first in a series of the late author's Discworld novels.

Adapting the book for cinema has been a long-time ambition of Sir Terry's daughter.

She said: "I've loved the Jim Henson Company's work all my life, so it's a great honour to team up with them and bring Wee Free Men to the big screen."

Brian Henson, chairman of The Jim Henson Company, said: "As a family owned company, we fully understand the importance of legacy properties.

"The Discworld series is a richly developed world with devoted fans, myself included, and there is no-one better than Rhianna to bring Terry's beloved project to life on the big screen."

Sir Terry died aged 66, eight years after being diagnosed with Alzheimer's disease. He wrote more than 70 books during his career.

He also introduced a BBC documentary entitled Terry Pratchett - Choosing to Die, which won an award at the Scottish Baftas.