JODIE Foster describes her latest character on the big screen as an "amazing ball of contradictions". She is talking about her role in The Mauritanian, which sees her playing tenacious real-life lawyer Nancy Hollander.

Directed by Scottish film-maker Kevin Macdonald, who made The Last King of Scotland and the political thriller State of Play, the movie has been blazing a trail through awards season, with Foster having already won the best supporting actress prize at the Golden Globes.

It's also in the running for gongs at the forthcoming Bafta film awards, with nominations in the best film category and star Tahar Rahim nominated in the leading actor category.

Rahim, who was recently seen in BBC's The Serpent, portrays Mohamedou Ould Slahi in the movie, which is based on Slahi's best-selling memoir, Guantanamo Diary. The book details Slahi's time in the notorious detention camp, where he was imprisoned in 2002, held for more than a decade without charge and only formally released in 2016.

"It was an instant yes," reflects Oscar-winner Foster, 58, on taking on the role of Slahi's defence lawyer, Hollander.

"Because I read it, couldn't stop reading it, was fascinated, and really wanted to be a part of telling Mohamedou's story. But it was a very long script, and it went off in a lot of different directions so there was some work that needed to be done, just to shape it and focus it.

"I think that's really a testament to Kevin Macdonald, the director, that he was really able to identify the important part of the story and to keep it moving in that direction; the important part was really Mohamedou's story, just to prioritise that."

A military prison, the Guantanamo Bay detention camp in Cuba was established during George W Bush's administration in 2002, following the devastating 9/11 terror attacks in the US in 2001, which had prompted the 'War on Terror'. And it is against that backdrop and political climate that Slahi's story is set.

"It wasn't an instant yes for me," says Macdonald frankly as we speak over Zoom. After reading the book he says that, while he thought it was a "fascinating piece of testimony from inside the prison system, I couldn't see really how to make it into a film".

The 53-year-old explains: "I thought there had been a lot of documentaries, there'd been a lot of books about this subject and I wanted to make something that would reach a wider audience. It was only when I talked to Mohamedou himself on Skype that I became certain I wanted to do it because he was an amazing character.

"He wasn't angry, he wasn't bitter, he was full of (a) kind of joy almost and (had) a great sense of humour and he's an incredibly, intelligent and fascinating man and I thought 'Oh, that's what I want to make a film about, about this character'."

For Foster though, playing Hollander, who is still a practising criminal defence lawyer in the US, it meant taking "some licence".

She says: "Nancy is this amazing ball of contradictions. She wears bright red lipstick and bright red nails, likes black leather, and race cars, and yet she's this very sombre, measured, calm presence with a steeliness to her, always suspicious, always looking around, noticing.

"But with that being said, I did take some licence. My Nancy is a lot meaner than her Nancy, she's a lovely person. My Nancy is not so lovely. especially in the beginning (of the film).

"I really wanted to show that she changed over time and that Mohamedou as a person, this extraordinary person she was faced with, that in ways allowed her to become more vulnerable and soften up, so that she could care for him."

French star Rahim, 39, recalls his first meeting with Mohamedou on Skype.

"I was shooting abroad, I wanted to meet him physically but I couldn't. This meeting was memorable to me because I had an idea of Mohamedou from what I've seen and you know he was as a good man, but when I met him it was above this.

"He was funny, full of life, generous, he would play music, (he was) very interested in you, who you are, asking about my family, so gentle, it was almost unbelievable that he's been through hell.

"I started to talk with him and it was great. I had to ask him some questions, some touchy questions, and then he changed and I felt that he was very sad, as if he was going back there instantly in Guantanamo being tortured, so I stopped. I felt bad, I felt stupid.

"I understood at this very moment that the best way for me to catch his personality and his spirit was to talk with him, spend time with him and observe him so I can really make him live inside of me."

He also felt an enormous sense of duty to the real-life person, he explains.

"I didn't want him to be disappointed or to feel diminished or in a way betrayed, so I went all in. I was like, the only way to make it, to bring authenticity on screen was to get as close as possible to what he has been through, and I did it. I wanted to do him justice".

For Macdonald, there was a balance to be struck on screen.

"In the end it has a rather uplifting message actually," he says, "but sometimes, in order to get a really powerful effect in a film, you need to take the audience to the edge of their comfort levels. And that's I guess what we do in this film, but the impact of that is then felt later on."

There is also an important message about the importance of the rule of law, he adds.

"I think that governments make terrible decisions when they are frightened or when their populace is frightened and that probably goes for what's going on right now with Covid in some countries.

"It goes on with the sort of nationalism we saw in America under [former President Donald] Trump. A lot of that was about fear.

"He weaponised fear - talking about rapists from Mexico and [people] coming to steal your jobs.

"So obviously the overriding message of this film is about the importance of the rule of law, which is not a very sexy thing, I suppose, to have as the central theme, but it is incredibly important to our lives. Without the rule of law, nightmares are bred."

Amnesty International has launched a global campaign calling on American President Joe Biden to close Guantanamo permanently. The organisation says that around 40 men are still imprisoned there, with the majority never charged with a crime.

In February this year, Mr Biden's aides launched a formal review of Guantanamo Bay but the detention facility is still open.

The Mauritanian streams on Amazon Prime from April 1.