'Stillwater': Camille Cottin praises 'amazing' work of her nine-year-old co-star (exclusive)

Watch: Camille Cottin praises child star of Stillwater

Camille Cottin says it was "amazing" to work alongside nine-year-old child actor Lilou Siauvaud in Stillwater — and she was every bit as impressive as Oscar-winner Matt Damon.

The film, directed by Tom McCarthy, stars Damon as Bill Baker, who is the father of an American student (Abigail Breslin) imprisoned in Marseille for the murder of her girlfriend.

While attempting to clear his daughter's name, Bill meets French theatre actor Virginie (Cottin) and bonds with her precocious little girl Maya (Siauvaud).

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"Honestly, that child is so amazing. I have to say I was as dazzled by Matt's performance as by Lilou," Cottin tells Yahoo Entertainment UK.

She adds: "The two of them were so in tune. Lilou has no rupture. There's no break between the way she is and the way she acts.

"When they said 'action', there was not a single change in her attitude and the way of being and the way she listened was just like in reality. This was honestly fascinating.

"And then I had this incredible actor completely disappearing behind his goatee and being just his character. For me, I was the one who was being taught."

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Cottin had a lengthy career in French theatre and TV before making her English-language film debut alongside Brad Pitt and Marion Cotillard in the 2016 thriller Allied.

She says it was special to be able to premiere Stillwater in her home country at the Cannes Film Festival, as well as screening the film for cast and crew in Marseille.

"It was a very different atmosphere [in Marseille] but very moving," she says.

"I didn't cry at the premiere in Cannes — although I was very moved — but I cried in Marseille when Tom said 'can the people who've been working on the film stand up?' and we had like a hundred people standing up and clapping and whistling. That very much brought me to tears."

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Cottin's next project is the Ridley Scott historical crime tale House of Gucci, in which she will appear alongside Lady Gaga and Adam Driver.

Stillwater is in UK cinemas now.

Watch: Trailer for Stillwater