Sienna Miller walks the Cannes red carpet with daughter Marlowe

Sienna Miller has walked the red carpet at the Cannes Film Festival with her daughter Marlowe Ottoline Layng Sturridge.

The 42-year-old actress, who was born in the US but brought up in the UK, has been promoting her new film Horizon: An American Saga, directed by Kevin Costner.

Miller - who will appear in this film and its next instalment - plays East Coast settler Frances Kittredge, who moves to the Horizon settlement with her husband and two children.

Miller wore a pale blue floor-length gown, while 12-year-old Marlowe wore a white dress with a large pale pink bow around the waist for her red carpet debut.

Miller gave birth to Marlowe, whose father is The Sandman star Tom Sturridge, 38, in 2012.

She had a second daughter earlier this year with The Crown actor Oli Green, who also attended the premiere.

Miller and Green, 27, met at a Halloween party thrown by a mutual friend and have since moved to London together.

Costner - who not only directs the film but also co-wrote and stars in it too - had plenty of family support on the red carpet.

The 69-year-old Hollywood star brought five of his seven children - Annie, 40, Cayden, 17, Grace, 13, Lily, 37, and Hayes, 15. The latter makes his screen acting debut in the movie.

Horizon: An American Saga spans four years of the Civil War, from 1861 to 1865, and is described by the studio behind it, Warner Bros, as an "ambitious cinematic adventure" telling the story of the United States of America "through the lens of families, friends and foes".

Brace yourself for a three-hour epic - and more to come

The two-part western - of which this is the first chapter - received a 10-minute standing ovation when it premiered on Sunday.

Costner also says he has scripts ready for two further instalments in the story, which would extend the epic to four parts if commissioned.

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The Yellowstone star, who first pitched a version of the movie back in 1988, has plenty at stake in the project, and personally financed around $100m for the film and its sequel.

He will be hoping to emulate the success of his 1990 directorial debut Dances With Wolves, which he also starred in and produced. The movie was a box office hit, winning multiple Oscars including best picture and best director.

Horizon: An American Saga runs for over three hours and will come to UK cinemas at the end of June.

It also features Avatar star Sam Worthington, Donnie Darko actress Jena Malone and Owen Wilson's brother Luke Wilson.