Outlander star Sam Heughan will star as Paul Newman in a film about the lives of author Roald Dahl and actress Patricia Neal.

The as-yet-untitled biopic will see Downton Abbey’s Hugh Bonneville playing the children’s writer while Bodyguard’s Keeley Hawes will play Neal.

Neal, who starred in films including Breakfast At Tiffany’s and The Day The Earth Stood Still, was married to Dahl for 30 years between 1953 and 1983.

She co-starred with Hollywood actor Newman in 1963 drama Hud.

The biopic reportedly begins in the early 1960s and follows Dahl’s struggles to write some of his best known works, including Charlie And The Chocolate Factory.

Scottish actor Heughan, 39, said he is “lucky to be part of this beautiful movie”.

He added: “Paul Newman was immensely talented, generous and an American icon. So fortunate!”

Hawes commented on Instagram: “Thank you for being brilliant and the perfect Mr Newman!”

The Dahl and Neal biopic is being directed by British filmmaker John Hay and will tell the story of the couple’s tumultuous marriage.

Dahl’s best known books include James And The Giant Peach, Charlie And The Chocolate Factory, Matilda and The Witches.

He died aged 74 in 1990.

Neal was 84 when she died in 2010.