I am speaking to the Finnish film-maker Juho Kuosmanen, director of the prize-winning new film Compartment No 6, under conditions very different from our previous encounter at last autumn’s London film festival. That was a garrulous face-to-face chat about this film in the amiably chaotic surroundings of his central London distribution company. Now it’s our two subdued faces side-by-side on a computer screen, as we dwell on the fact that the phrase “third world war” used to be an essentially comic phrase, or category error, or a piece of intentionally ironic numerical wrongness like “sixth sense” or “fifth horseman of the apocalypse”.

Compartment No 6 is set in the spring of 1998, the era that Kuosmanen says was Russia’s hopeful moment, when Boris Nemtsov could have taken over from Boris Yeltsin as president. Laura, played by Seidi Haarla, is a lonely Finnish archaeology student, who is getting over an affair with her professor in Moscow, and takes a colossally long and arduous train journey to Murmansk in remote north-western Russia to study rock drawings there. She sits herself down in scuzzy compartment No 6, and finds herself opposite Ljoha, played by Yuriy Borisov, a drunk and obnoxious Russian guy who instantly starts pestering her. He appears awful. He is awful. And yet after this meet-uncute it becomes clear that he may not be so awful. It’s a wonderful and thoroughly engaging film whose romantic element remains complex and elusive right to the very end of their epic train journey.

Compartment No 6 has achieved new kinds of meaning in the light of current events: a typically boorish Russian menaces someone from a vulnerable neighbouring country, but who as an individual attains a kind of redemption. Kuosmanen, who has taken a family of refugees from Kharkiv into his home, is sombre: “I have colleagues and friends in Ukraine and Russia,” he says. “Some are still in Kyiv, and some have moved on. Our Russian co-producer, Natalia Drozd, has left Russia because she is an outspoken opponent of Putin.

“My chief emotion about the war is a fountain of frustration. Because there is nothing new in it. This war has been going on for eight years. This shouldn’t be surprising.”

As for the Russianness of his film, that is a difficult issue. “It was very well received in Russia. They were amazed that a foreign film-maker could so sympathetically represent Russia and Russians. Because Russians keep getting told by paranoid nationalists about Russophobia and that all foreigners are a threat.”

Before the war, our global anxiety was all about Covid and the lockdown; at our first meeting, Kuosmanen confesses he didn’t mind that. “Just at the end of shooting, the border between Finland and Russia was closed and we were ordered to go home. I had to spend two weeks in isolation. I loved it! When you’ve spent two months in intense contact with people it feels so nice to be alone. We were in a lucky situation to finish shooting when we did. I was almost annoyed to be so lucky. Also, the Russian rouble was losing its value so we got some benefit out of it.”

He says the idea for Compartment No 6 came to him about 10 years ago. “I discovered the novel [by Finnish artist and author Rosa Liksom] and I could really see and smell those scenes. I had been travelling in Russia a lot. I took lots of pictures. Lots of strong colours. Strong textures.

“The Finnish film historian Peter von Bagh, a teacher of mine, wrote a book called Junassa, or On the Train, about films that take place on trains. It must have been an influence. He was crazy about films and crazy about trains! I love trains. It’s the best way to travel, especially in Russia because you do these long trips and you meet interesting people. You just don’t talk to people on plane journeys.”

Critics are calling the film the Finnish answer to Before Sunrise – the indie US movie franchise by Richard Linklater with Julie Delpy and Ethan Hawke having a serendipitous love affair on a European train journey. Does he feel comfortable with the Linklater comparison? “I love those films, I don’t mind at all!,” he says, laughing. “The biggest thing I got from them was the idea that nothing can happen and it’s still interesting. But the more obvious influence was Lost in Translation.” This is Sofia Coppola’s movie about characters played by Bill Murray and Scarlett Johansson in Tokyo, finding a connection in their loneliness. “You feel so happy for them, but at the same time you really hope they don’t have sex.”

Before Compartment No 6, Kuosmanen made a rather amazing boxing-movie-slash-romantic comedy based on a true story: The Happiest Day in the Life of Olli Mäki, shown at the Cannes film festival. Mäki was a Finnish boxer who in 1962 electrified the country by getting a shot at the world featherweight title, fighting on home turf against visiting American champ Davey Moore. He was horribly beaten, but it was the happiest day of his life because he had found love.

“Mäki was an allegory of the situation I was going through,” Kuosmanen says cheerfully, explaining that he felt just like the Finnish underdog, trying to impress everyone in the brutal boxing ring of Cannes’s cinematic reputation and going up against the best in the world. But he has been a recurrent winner at Cannes, getting a prize in the Cinéfondation section for an early short film and most recently the Grand Prix for Compartment No 6 in 2021. Climbing the red carpet steps was a scary moment: “You feel like you don’t belong there, because this is for the stars. But then you realise that this is all just real life, and the red carpet is such a small part of it.”

Both of his movies are about Finland going up against the big powers, I suggest. In one, the US, in the other Russia. He nods: “Finland is always very aware of what people in the world are thinking about Finland. We are not part of Scandinavia – we are always the dumb little brother to them. Maybe in Finland, you are always trying to be bigger than you are.”

In the end, they are both love stories. Is he a romantic? “I’m romantic and I’m nostalgic. Both things I would prefer to say I’m not. But I’ve learned to accept it.” Now he is working on another romantic drama from Finnish history: a story about the feminist author Minna Canth.

Kuosmanen tells me that he has come to the movies after a long creative journey in which he has worked in TV, theatre and even opera, but in the end these are for him subordinate to cinema. “Film is much more serious. I’m worried that I may love it too much!”

• Compartment No 6 is out in the UK on 8 April.