Tilda Swinton has said starring in The Eternal Daughter was a passion project both she and director Joanna Hogg had spoken about making for many years.

Scottish actress Swinton, 61, plays both mother and daughter in the psychological mystery which also stars Carly-Sophia Davies and Joseph Mydell.

Arriving at the film’s UK premiere at the BFI London Film Festival, Swinton spoke about her long-term friendship with Hogg, who directed and wrote The Souvenir films.

She told the PA news agency: “Joanna is literally my oldest friend. I don’t mean she’s the oldest person I know, I mean she’s known me for the longest ever and this is a project we have talked about for many years and it’s very personal to both of us.

“It’s about our mothers and us. We’ve talked about being us and our mothers being young since we were 10 so it would be impossible to resist carrying it through to making a film. It’s super personal.

“Like all really deep stuff it is incredibly liberating. It might be about something that feels heavy to the audience but the heavier it is somehow the lighter it is to make.

“We had a beautiful time and in many ways it was the perfect shoot that we’ve ever experienced, either of us and I’d like more of that.”

Swinton also spoke of her hopes for people who had seen the film.

“I think those of us who have finished seeing the film who have mothers it’s a good thing to call them, and those of us who have daughters it’s probably a good time to call them.

“If you haven’t got either then I just think forgiveness, forgiving oneself for not being the perfect ideal of a daughter or ideal of a mother. It’s a ghost story at the end of the day and it’s always nice after a ghost story to get cosy.”

Hogg said it was “difficult to put into words” what the project meant to both Swinton and her.

She told PA: “I clutch my heart because it has brought us even closer, if that’s possible.

“We’ve known each other since we were 10 or 11 and this was the first time we had worked together as ourselves on something that is very close to both our hearts and the conversations we had when we were making the film and just all the ideas that have gone into it connects us so much so it was a joyful experience despite the sad subject matter.

“I feel no one has seen Tilda in this way before, she really risks so much in playing the two characters. Everything is very stripped back, raw and vulnerable. I feel very emotional about it.”

Hogg has mined her own life for material and inspiration for much of her filmmaking over the years.

She said: “It’s a very dark film and it’s a very personal film.

UK premiere of The Eternal Daughter – BFI London Film Festival 2022
Tilda Swinton on the red carpet (Ian West/PA)

“My mother was very much alive when I first thought about making this film, her death occurred when we were editing the film and I was really hoping that she would see it and she was actually looking forward to it and she even had many ideas that are in the film.

“It was her idea the name of the hotel, there are a lot of connections with my mother in terms of ideas and creativity of the film.

“In a way I was mourning her loss before the loss, the film I was putting myself a little bit into the future and I’ve always dreaded that moment when my mother was no longer, it is something that has haunted me from a very young age.

“This film has haunted me since 2008, I have wanted something about my relationship with my mother so I feel very sad that she’s not here to see it right now.”