If your mother has been an actress and your grandmother’s been an actress, there’s certainly an encouragement. My father wanted me to be a painter, so my mother helped me on the secret side. She got a lot of stick for that. But in the end my father adored me in films.

Had it all worked out with John Barry [her first husband, whom she married at 18], I would never have been curious to know what was going on anywhere else. I would have just gone on being his wife, I would have been delighted. But because he went off with someone else, and I was left with Kate [their daughter, who died in 2013], I had to find a job quite fast.

I learned French off a tape recorder and from what Serge [Gainsbourg] would teach me, which was slang. Everybody laughed. I don’t know how much I genuinely wanted to get better at it or how much I wanted to make all French people laugh.

I did comedies and sexy pictures. The sexy pictures are a bit depressing when you come out of a wonderful concert and somebody turns to you with nude photographs for you to sign. I’d quickly sign over the bottom. It happens more and more now because they get them off the internet.

I was a rather bad version of Jean Shrimpton. That’s who I wanted to look like. When I look back at photos and see myself in Blow Up or La Piscine, I’m not very interesting.

We were on a television programme just before Serge died. They asked me, what’s he to you? And I said, “toi”, which means “you”, a stupid answer, but it was all I could think of. And then they asked Serge what I was to him, and he said “émoi”. I thought he’d said, “et moi”, but he said émoi, which means to be moved, emotion. I think that’s why he wrote for me. Those songs were messages. They’re really quite strange to sing.

Je T’Aime… Moi Non Plus, with no make-up and dressed like a boy – that was pretty gorgeous. And Serge was gorgeous, too. It was the prettiest time.

When I saw pictures of Glenda Jackson at 80, I thought, ‘Oh wow, if I could be like her!’ It’s probably to keep your own morale up, but you find people getting more and more gorgeous the older you get.

I’m not curious, but I’ve got very curious friends. I’ve got a friend who takes me to the theatre three times a week and a girlfriend who takes me to see three movies in a night, sometimes. A few years ago I realised how much it helps to go into other people’s stories. I’m a great follower. If someone’s got a great idea of what to do then I simply love it.

I was 40 when I did my first concert, at the Bataclan. I cut my hair off like a boy, I wore men’s clothes. I only wanted people to hear the music and the words. It was fantastic. And it was so frightening. Serge was there and he kept lighting his cigarette lighter to make everybody put their lighters on when I sang Fuir Le Bonheur. All this began at 40. People should never think it’s all over when you’re very young.

Jane Birkin’s first studio album in nine years Birkin/Gainsbourg Le Symphonique is out now