Just imagine the pitch. “I want to make my debut film about a girl who falls in love with a funfair ride. Um, that’s it.” But, however improbable it may seem, Zoé Wittock didn’t just get Jumbo bankrolled, the film was also screened at Sundance. And it’s every bit as strange, and quite a bit richer than you might expect.

Jumbo tells the story of Jeanne, played by Noémie Merlant, who lives with her sexed-up single mother near an amusement park, and also has a job there as an after-hours cleaner. One night, while spit-cleaning the knobs on a new fairground machine, Jeanne realises she has fallen in love with “him”. And so begins a giddy rites-of-passage story, with the intoxication of flashing lights and the sensuality of oil standing in for the dopamine rushes and tentative bodily exchanges of first love.

Wittock, the daughter of a Belgian diplomat who spent her early childhood in the Democratic Republic of the Congo, took the film’s title from the Swahili word “jambo”, which means hello. She was inspired to make it after reading about a woman who “married” the Eiffel Tower. “I was like: ‘OK, well, that is crazy.’ But it just kind of stuck with me. Whenever I mentioned it to friends after that, it would just create so many debates and interactions and would divide people so strongly that I felt I had to meet this woman.”

When she eventually tracked down Erika Eiffel, she seemed perfectly normal. “I was expecting someone who was a freak, or on the margins of society, but she was really warm, soft, welcoming and almost banal, which made me wonder how she could have made such extreme choices and be so strong and so open about them. I started writing this story, because I needed to understand her.”

Today, objectophilia and “objectum sexual” people are relatively well known. Individuals have spoken publically about their infatuations with the Berlin Wall or the Golden Gate bridge, while last year a Moscow teacher “married” her briefcase. Eiffel has even set up a support group, OS Internationale. But in 2012, when Wittock started researching the subject, it was so little understood that she was turned away by the first psychologists she consulted.

Some academics believe there is a correlation between OS and autism. Jumbo hints early on that Jeanne’s issues were to blame for her father’s disappearance from her family, but at its heart this is a coming-of-age story that allows you to sympathise with the anxious exasperation of Jeanne’s mother (Emmanuelle Bercot), while sweeping you giddily into its glamorous nocturnal orbit. Compared with the supervisor, who tries in vain to strike up a relationship with Jeanne, Jumbo is kind of virile, with his pulsing lights and his thrashing arms. There’s even a King Kong moment when he “rescues” Jeanne from a grisly end by nestling her in an upturned “hand”.

Casting Jumbo was not easy. After scouring amusement parks around the world, Wittock tracked down the perfect ride in France. “We chose this one,” she says, “because he had the perfect shape. He was big and impressive, but not huge, which would have made him really hard to film with humans.”

So how literally are we supposed to take the film? “I wouldn’t be able to quantify how much is a metaphor,” says Wittock, “because that’s really up to the person viewing the film. I wanted to keep one foot in reality and the other in fantasy. The metaphorical aspect is that it’s a romantic story that can be likened to romantic stories in which people don’t find tolerance because of how different they are, even though this is more extreme.”

Has Erika Eiffel seen the film? “Yeah, she has,” says Wittock who, on discovering that Eiffel lived in Berlin, invited her to watch it at the Berlinale film festival. “It was right before Covid hit, and there were 1,000 people watching the film, so she discovered it along with everybody else in the crowd. It was a very stressful moment, because I was afraid she might be offended. There are times when you can laugh in the film, and I was worried that she would take it too personally. But she was very emotionally involved with it. At the end, she cried.”

Ultimately, says Wittock, it is the story of an outsider – something her own itinerant childhood made her all too familiar with. “I hate putting people in boxes,” she says. “I always want to break those boxes. For me, it’s just a romantic story. I understand that it’s weird. But what can I say? There’s no harm done. I really can’t be the one who decides to marginalise a person like Jeanne for their choices. They’re their own people. It’s up to them.”

• Jumbo is in cinemas.