This is a snapshot of family life. Except that this is no ordinary family: Jane Birkin is one of the biggest icons of chanson, and a deeply transgressive artist. Charlotte Gainsbourg, her only child with the late enfant terrible of French music Serge Gainsbourg is no different. The two adult women connect in more ways than one in this deeply personal, homemade type of documentary.

In fact, Jane Birkin’s family has long dissipated. She lives on her own somewhere in the bucolic yet not particularly glamourous coast of Britanny. She had three daughters, each one with a different man. The eldest one Kate Barry committed suicide years earlier. Lou Doillon is nowhere to be seen, her name only briefly mentioned in passing. Charlotte herself seems to know very little about her mother’s current life, instead allowing the septuagenarian to open up her heart in front of the camera, revealing her malaises, fears and a lingering sense of guilt.

It is clear that Jane suffers from some sort of depression. Her mental health began to deteriorate since Kate took her own life, and an addiction to sleeping pills seems to have defined her existence since. “Sometimes I sleep until 15:00”, reveals the still beautiful and charming singer and actress. The house in which she lives is cluttered with furniture and bric-a-brac, suggesting an indolent lifestyle. She confesses to being a hoarder: “I can’t get rid of anything, instead others have to do it for me”.

Despite the mental challenges and the apparent solitude, Jane is never camera-shy. She concedes that she still gets a thrill from being filmed. She is no longer a teenager prancing around naked in front of a photographer’s lens, as in Antonioni’s Blow-Up (1966), but she is still beautiful, her quiet gaze just as charming. She fears, however, that her lips will soon disappear as it happened to other member of her family at old age.

In one of the movies most powerful moments, Charlotte and Jane visit the house where they lived for 12 years with Serge. For some inexplicable reason, the dwelling has been barely touched since the musician passed away three decades ago. It has become some sort of “Pompeii”, Jane jokes, every little object fossilised. Even perfumes and tinned food remain largely intact. Unlike Jane, who has been deeply affected by senescence.

Die-hard fans might be slightly disappointed that their diva barely gets behind the microphone. There is a quick rendition of Johnny Jane and Ces Petits Riens, but that’s about it. There are also extracts from a couple of songs by Charlotte Gainsbourg. The two women encountered copyright issues, they reveal in one of their conversations. So they settle for Bach instead, convinced that the 18th century German will not sue them.

Surprisingly, the question of national identity is never addressed. Jane Birkin is a British-turned-French artist. She gave up Britain in favour of Brittany. She prefers French to her mother tongue. In fact she utters no more than one or two sentences in the language of Shakespeare. Is that thanks to Serge Gainsbourg, her first French husband and an overpowering uber-artist? What about Charlotte? Does she too embrace her French identity ahead of Britishness? Those questions remains unanswered.

Jane by Charlotte premiered at the 69th San Sebastian International Film Festival. It also shows at the 25th Tallinn Black Nights Film Festival.