Before Midnight takes the love story that began 19 years ago in Before Sunrise full circle

Ethan Hawke, Julie Delpy and the director Richard Linklater reunite for Before Midnight.

Ethan Hawke and Julie Delpy in Before Midnight. Despina Spyrou

When Ethan Hawke, Julie Delpy and the filmmaker Richard Linklater collaborated on 1995's Before Sunrise, no one expected the low-budget romantic drama to spawn two sequels, Before Sunset and, released this week, Before Midnight.

The “accidental trilogy”, as Linklater calls it, began with Jesse (Hawke) and Celine (Delpy) sparking romantically after meeting on a train in Europe. Nine years later, the second instalment reunited them in Paris, their circumstances now complicated by Jesse’s marriage. It finished with the possibility that he might leave his wife for Celine.

Almost a decade on, Before Midnight reveals what happened next, in what may be the last screen outing for the transatlantic characters. That said, Hawke and Delpy say that they could make another trilogy, with the same gaps in between films, and by the end still be younger than the actors in Amour – Michael Haneke's Oscar-winning drama about a couple dealing with old age.

“This is turning into kind of a life project about romantic love,” says Hawke, who not only acts in the films but, like his co-star, contributes to the writing. While experiences from their real lives slip into the mix, the actors say that they are not Jesse and Celine.

“The three of us wrote all three of these movies and Rick [Linklater] created Celine and Jesse as much as us,” says Hawke. “It’s like half me, a quarter Julie and a quarter Rick. Something like that.”

Delpy describes the planning of each film as “logical” and “organic”. “We think: ‘OK, nine years. What happens to people when they have been together for that long?’”

On this occasion, they first had to decide whether Jesse's feelings for Celine at the end of Before Sunset were sincere.

"I watched the film again and it seemed really clear to me that he is madly in love with Celine and he is going to do whatever it takes to keep her," says Hawke. "Once you've made that decision, that they're going to be together, the question is: how did the divorce go? How is that working out?" The Greek-island setting of Before Midnight is idyllic, but the romance of the first film, in particular, has given way to clear-eyed reality. The middle-aged couple have got what they wanted – but do they still want it? When Jesse suggests moving the family from Paris to Chicago, to be closer to his son from his failed marriage, resentments surface, leading to an explosive argument that could break or strengthen their relationship.

“It’s kind of a metaphor for our own working relationship on this,” says Linklater. “Julie and Ethan and I now have our own long-term relationship that has its own little moments where you take a breath and go: ‘OK, can we do this? Is it worth it?’”

That feeling of effortlessness is a product of the chemistry between the actors and the hard graft that goes into creating an illusion of spontaneity on screen. The dialogue flows realistically, but Linklater dislikes improvisation and so every pause and overlapping line has to be painstakingly mapped.

“We make sure that what we’re writing is written in a way that we can make it feel natural,” says Delpy. “Sometimes writers don’t write like it sounds. But luckily we’re actors, so we know what would also sound right.”

Although Hawke and Delpy have contributed to the scripts of all three films, union rules prevented them from being listed as co-authors on Before Sunrise – it wasn't until Before Sunset, which earned an Oscar nomination for its screenplay, that they received a writing credit. Both praise Linklater for boosting their confidence as writers.

Delpy says: "I had written a screenplay before Before Sunrise that I gave to a famous writer and he said: 'You're very pretty. Please don't write.' After Before Sunrise I was like: 'Oh, I can write these things that people really like.' So it gave me confidence to write again."

They’ve clearly all enjoyed working together. So is this really the end for Jesse and Celine?

“There might be another one, who knows?” says Linklater, teasingly.

Before Midnight is out in cinemas now