LAST year Freya Mavor didn’t go home for Christmas. She didn’t sit around the family table eating turkey and Brussels sprouts, she didn’t open presents, didn’t get messy with a bottle of Prosecco and a box of Celebrations. Didn’t, in short, do anything that the rest of us do at this time of year.

No, last Christmas Freya Mavor went to Costa Rica to learn how to surf.

Mavor had been working for seven months solid, on three jobs back to back and all she asked for Christmas was to have some time to herself.

“All I wanted to do was be in the sea,” she explains, “and it was the one slot I knew I had time, so I just thought: ‘I’m going to throw myself into the waves and get battered by some swell.’

“I like challenging myself. I like confronting myself. I think it’s an interesting thing for humans to do. To force themselves into uncomfortable situations.

How uncomfortable, though? Did she end up hitting the rocks? “I did not. I did get hit on the back of the head by a board.”

Going to Costa Rica for Christmas could be said to be a very Mavorian thing to do. The 25-year-old actor probably best known for making her debut in the Channel 4 teen drama Skins and singing in the big-screen Proclaimers musical Sunshine in Leith, is not one to do the obvious. In her life or in her art.

She doesn’t have a TV, she writes poetry and makes poetry videos (and doesn’t feel any need to make any self-deprecating apology for the fact). She speaks French, acts in French too. She makes music, but only, she says, for personal enjoyment. “I don’t have fierce ambitions of becoming a singer in a punk band but music’s a huge part of my life.”

And until recently she had never watched an Agatha Christie movie or TV adaptation in her life.

But this Christmas she is going to sit down with her family in Scotland on Boxing Day and watch The ABC Murders. That might have something to do with the fact that she’s appearing in it.

Mavor is one of the stars of this year’s BBC Agatha Christie-thon. The latest of Sarah Phelps’s reboot-stroke-reinventions of the Christie library, The ABC Murders is a late-period Poirot story starring John Malkovich, Rupert Grint, Eamonn Farren and her fellow Scot Shirley Henderson, that is here reimagined as a political thriller set in a vision of 1930s Britain that’s full of xenophobic malice and looks like it has been dipped in tea for about a year. It’s a grubby, dark, anything-but-cosy vision of a disunited Britain.

And John Malkovich, who plays Poirot, doesn’t even sport a moustache.

Mavor plays the part of Thora Grey, who in the opening episode spends most of her time floating about a country house and on the margins of events. No spoilers but that will change in the subsequent episodes.

But her main contribution to episode one, though, is to sit at a table and have wine thrown in her face by Tara Fitzgerald.

Well, I say wine, but ... “It was like Ribena with extra food colouring in it,” Mavor explains. “Sticky, very sticky. And it was summer, so I was attracting a lot of wasps. The glamour of film-making,” she says with a smile.

Pretty, pale, and gently Scottish-accented, today Mavor is sitting in New Broadcasting House in London wearing a tartan skirt and her natural Celtic colouring. On the floors beneath, the BBC news room is buzzing with the day’s latest Brexit catastrophe. This is November; so, we’re talking several Brexit crises ago now.

When you go to France, Freya, what are they saying about Brexit? “At the moment their mouths are hanging down to their knees. They can’t quite believe … I’ve grown up between France and here and I feel very European. The EU was made after the Second World War to unite us, so it feels absurd and grotesque and it just feels terrifying plunging into something where there is no clue about the outcome. It’s very frightening. And also frightening to see how we are reflected to the rest of the world.”

The last time I met Mavor was in Belfast in the summer of 2017 the day after the last general election. I was sick (you really don’t want to know the details). She had just started shooting a film about the German goalkeeper Bert Trautmann. Then she was articulate, clever, open and entertaining company. That hasn’t changed.

Mavor is in full publicity mode when we meet. After this she is going back to Paris to promote her new French film Jean-Francois Richet’s Emperor of Paris (or, as she calls it, L’Empereur de Paris, in a perfect French accent).

But today it’s Agatha Christie. Not something, Mavor admits, that she knew much about before shooting The ABC Murders. “I have to admit I had never seen an Agatha Christie film or TV show. I had never read an Agatha Christie book.”

So, then, why did she want to do it, you might ask? Because she could see it was going to be different, Mavor says. “I associate Agatha Christie with family dramas and people gathering around the telly set and guessing whodunnit. And this seemed quite different.

“And I’m not going to lie. John Malkovich. Yeah, any excuse to be in the same room as him I will take.”

There are worse reasons. But down to brass tracks, Freya. Here’s what we need to know. Do you yourself have a police record? “I couldn’t possibly comment,” she laughs.

Well then, if you had to commit a murder how would you do it?

“Ooh, I’d probably want to be quite inventive. I’d probably go for something exciting like drowning someone in slurry.” She thinks about this for a moment before conceding: “It could be messy.”

Freya Mavor’s earliest Christmas memories sound like a Scottish spin on a Kirstie Allsopp festive TV programme. Growing up in Edinburgh, her mum Judith was an opera singer and also keen on crafts. “My mum would make little felt Christmas decorations. We had bizarre Christmas decorations.”

How weird?

“A felt version of peanut butter and jam toast … Because we spent a winter in the States where that was all we ate.”

Edinburgh might have been home but Mavor’s childhood was a peripatetic one, with the family moving around and living at various times in the US, Turkey and France, of course. Mavor moved there on her own when she was 19 (to Paris, to be exact) and she still spends half her working life there.

The idea of constant change is something that she seems to have embraced wholeheartedly. Ask her what kind of actor she wants to be and “versatile” is the first word she comes up with.

The other word she offers is “unapologetic.” She wants to claim ownership of her career and her image.

“There is something really interesting as a woman about owning yourself and the way you look and all the terrifying pressures that can come into this industry.”

She’s felt those pressures, then? Of course. We all have, she says.

“For a lot of people there’s a sense of what you should be, what you should look like. I think everyone feels a societal pressure to be living your perfect life, which is just unachievable. And a ridiculous aspiration.”

Her heroines, she says, are actors like Lesley Manville, Annette Benning and Tilda Swinton, “people who are powerhouses and have a lot of integrity.”

In 2018 we possibly have a better idea of what that entails. What has changed since the last time we talked, I remind her, is the context. The emergence of the #Metoo movement in the wake of allegations made against Harvey Weinstein and others has given us a greater insight to the challenges women face in the film and TV industry. The terms of debate have been changed as a result.

That’s a good thing, she says. “Conversations are being had that weren’t being had before and I think it’s giving a voice to people who, before, if they felt uncomfortable in a situation, would not speak out because then they would be scared of losing their position or not being hired or being ridiculed.”

I note from her IMDb listing that she has made a film with Kevin Spacey about Gore Vidal before allegations about his actions emerged in public. She gives an exasperated shrug when I bring it up.

“It was a shock to everyone. It was devastating to the victims and devastating making a film that involves hundreds of people and the actions of one person having that effect on hundreds of people’s work.”

Are we ever going to see that film? “I’ve no idea.”

There are other issues in play too, of course, she tells me. Such as? “The simple fact that we’re still not on equal pay with men.

“What does that say to a young girl? ‘You’re not worth the same as a bloke who’s the same age as you.’ It’s obscene.”

Well, is she hopeful about the future? She’s hopeful about youth, she says. “People being more eco-conscious and conscious of equality and sexuality. All that stuff is fantastic. At the same time,” she adds, “we’re in a very turbulent political place where it feels like extremist politics are in vogue. The easiest thing is to lose hope.”

The last time we spoke, I remind Mavor, she told me she was learning Spanish. How is that coming along? “Muy bien,” she replies, smiling.

So, Spanish cinema will be the next port of call then? “I’d love that. I’m a big fan of Almodovar. He usually goes for dark-haired beauties, so I’m not sure I’d fit into his aesthetic.”

Anyway, Freya Mavor is not going to France or Spain or Costa Rica for Christmas. She’s going to be with her family in Scotland watching herself on telly and wandering up Arthur’s Seat (“the thing I love most about Edinburgh”).

What’s the first thing you’ll do when you arrive back in Scotland, Freya? “It sounds awful to say but I have an Irn-Bru because I love it so much.”

Even the new recipe? “There’s a new recipe? Oh no.”

Christmas this year will be all about too much food and lots of games, she says. “I’m very competitive. To a fault. I’m slightly disgustingly competitive. I love a good game.”

So, it’s all Monopoly and Scrabble round the Mavor household? No, no, she corrects me. “Physical games. For my birthday we were wrestling each other. Tug of war. Rounders.”

Word of warning to anyone visiting though. If you do happen to beat Freya Mavor in a spot of Graeco-Roman wrestling it might be best to stay away from any nearby slurry pits. No point taking any chances, right?

The ABC Murders begins on BBC One on Boxing Day at 9pm and will run over three consecutive nights.

THE ABC MURDERS DIRECTOR ALEX GABASSI ON THE CHALLENGE OF ADAPTING AGATHA CHRISTIE

“To be honest the only Agatha Christie films I had seen were the 1976 Sidney Lumet version of Orient Express and the Kenneth Branagh last year. I didn’t know I was going to do this, so I went to see it for the sheer pleasure of watching an old-style look at it.

“Maybe I’d seen as a child Peter Ustinov, but I’d never seen David Suchet. And once I got this I didn’t want to see it. I hadn’t read the book before shooting either. I chose not to.

“I wanted to go back to the thirties and not have that nice, comforting, pleasing-to-the-eye visual style. You won’t find any art deco here. Everything is smoky, grimy, dirty.

“Why did I get rid of Poirot’s moustache? The first reason is I liked the way John looked. I just realised at his age, the bald head, the goatee …This was a nice beautiful design and was very symmetrical and was very Poirot without shouting it.

“Also, I didn’t want people to look back and think: ‘Oh, this is a character who’s done this case and that case.’ Forget about those cases. Now he’s an old vulnerable man. His best friend has just died.

I specifically did that to break tradition.”