Earlier this year, Kristin Scott Thomas was made a Dame, and she couldn't be happier with the honour.

"In my mind's eye, a Dame had always been someone with a couple of Jack Russells and a tweed skirt, but I love it. I think it's the most wonderful thing to be given," says the actress, who initially thought it was a joke that she was to be awarded the title.

"But I feel a bit nervous," she adds. "It's a sort of responsibility, because I have to step up to the plate and deliver the goods."

Considering her success and performances, it's perhaps difficult to imagine Scott Thomas ever feeling unsure of herself.

She's carved a career playing aloof roles, in the likes of Four Weddings And A Funeral, which earned her a Bafta, and Gosford Park - but that's acting, and she points out that people often assume she's going to be similar off-screen.

"Sometimes you have to work harder for people not to be afraid of you, so you have to be extra chummy," she says, jokingly raising her eyes to heaven and then breaking into a wide smile.

She laughs when one journalist's description of her being the 'go-to actor for elegant despair' is mentioned. "I quite like that actually... elegant despair. That sums me up, really."

The beautiful 54-year-old, who is today sporting a quiff, leather trousers and an oversized black coat, smiles often. She also sends herself up and is refreshingly candid.

Asked which film she's most proud of, she remarks: "There are so many things I'm proud of for different reasons. There's a Romanian film [1994's An Unforgettable Summer] I did entirely in Romanian. I'm incredibly proud of that but no one's seen it. I did a film with Nicolas Winding Refn [2013's Only God Forgives], where I went a bit mad and I'm proud of that. I'm proud of The English Patient [the 1996 film that earned her an Academy Award nomination]. So I'm mostly proud of things.

"I mean, there are a few things where I think, 'Oh dear, what went wrong there?'" she adds.

Perhaps at the mercy of the director's vision and final cut?

"No. Sometimes it's your own fault. You're just over-acting."

There's little chance of being accused of that in her latest movie, Suite Francais, in which she's on scene-stealing form.

The film is based on the bestselling book by Irene Nemirovsky and set in the fictional French town of Bussy during the early days of the German occupation.

It was years after the author's death, in 1942 in Auschwitz, aged 39, that her daughter found the two completed novellas, Storm In June and Dolce (which have been combined to make Suite Francais), along with an outline for a third called Captivity and the titles of the final two, Battles and Peace.

At the centre of the story is Lucile Angellier (Michelle Williams), who is waiting for news from her husband, a prisoner of war. It's the summer of 1940 and Parisian refugees are soon pouring into the small town, closely followed by a regiment of German soldiers who take up residence in the villagers' homes. Lucile and her domineering mother-in-law Madame Angellier (Scott Thomas) are joined by the refined German officer Bruno von Falk (Matthias Schoenaerts), and it's not long before a clandestine relationship between Lucile and Bruno ensues.

"In the book, Madame Angellier's described as being extremely religious, very tiny, bird-like and white-haired, quite different from how we've approached the character," says Cornwall-born Scott Thomas, who's lived in France since she was 19 and has worked on both English and French language films.

Madame Angellier might look different, but she remains as tough as she is in the book, prompting Bruno to joke that he should be the scary one.

"I figured that a mother whose son has disappeared, whose whereabouts you know nothing of, must be in an enormous state of anxiety," notes Scott Thomas, who has a daughter and two sons from a former marriage to a French gynaecologist.

"I think that people, when they're frightened or anxious, put up these terrible barriers to protect themselves. I think that's what she's doing. She's got a lot to lose, but there is a development in the way she sees the world, through the film."

She hopes she isn't as overbearing as Madame Angellier. "I'm afraid you have to ask them [her children] that, but I don't think I'm like that at all. I'm a bit of a pushover as a mother."

Scott Thomas, whose Royal Navy pilot father was killed in a flying accident when she was a child [her mother's second husband also died in a similar accident], went to boarding school before studying drama. She was reportedly told she wasn't good enough though, and moved to Paris to become an au pair - but decided to give acting another go and enrolled in drama school.

It wasn't long before the singer Prince cast her in his 1986 film Under The Cherry Moon. The movie was panned, but Scott Thomas received rave reviews and her career took off.

Her true passion is the stage, and it's where she returns in May to play the Queen in The Audience, a role that (fellow Dame) Helen Mirren has recently reprised on Broadway.

"I'm not quite sure what to bring to it yet. That's the whole point of rehearsal [which she starts this week] - to find out what's there. All I know is that it's a very good play and a fascinating character. We learn so much about government, about what it is to be this symbol, and what it is to be a woman in that position. I'm very excited about it."

She's had a more tumultuous relationship with film than theatre.

"I've been doing this for a long time and there are periods where you can't bear what you're doing and you're bored of it. And then there are times when you're interest is piqued and you want to do something," she explains.

"I regularly come into make-up in the mornings and say, 'This is the last film I'm ever doing', and then go and make 10, so who knows!

"I'm a human being, I'm allowed to change my mind."

:: Suite Francaise is in cinemas now