I wonder if it's possible for her to separate her idea of Serge from her idea of Paris?
"Not at all," she says. "Like Paris, sometimes Serge had the virtue of political incorrectness, or at least he never stood where you thought he would. For example, for all his provocation, he had a love of the police; he gave a great deal of money to the police widows' fund. At four in the morning no one else would be awake, so he went down to the police station at the bottom of the road with bottles of Krug champagne and sat up drinking with the night officers, telling Belgian jokes. He would come back with the gendarmes at incredible hours of the night, because he thought they should taste my Lancashire hotpot."
Family life must have been quite challenging?
"What we didn't realize was that it might be difficult for the children to be at school with their parents being on the radio like that, with Je t'Aime, and so on," she says brightly. "Serge did have a habit of chaining me up to radiators for photos, so that might have been quite hard for them, too. For us, though, it was very jolly."
By the time he died, Gainsbourg had had two heart attacks and had lost a portion of his liver, though he continued to drink and chain-smoke Gauloises as before. Does she believe she could have saved him from himself?
"I don't think I could," she says. "Everywhere he went in Paris people said, 'Hey Serge, this round is on me.' And he could not refuse. Someone called him a suicidaire optimiste, and that is very accurate. I don't think he thought he would die at 63, though. He thought he would have two or three chances at redemption first."
The great dislocation in Birkin's life occurred that week in 1991. When she was on her way to Gainsbourg's funeral, she heard that her father had died in England. She could not imagine a shock of pain like it. Sometimes, these days, she thinks of them together, the two men she wanted most to please. "They used to take their Mandrax together like two old owls," she recalls. "I'd say, 'Have you taken your sleeping drug?' and they would answer, 'No, non, non,' nodding off."
Her pain allows Birkin to forgive Gainsbourg anything, in retrospect. She left him after 12 years, pregnant with Jacques Doillon's child, and there is something unsettling about her subservience to his memory. "He was a permanent adolescent," she says at one point, as if this were the mark of his genius. Wasn't that hard to bear? "It was impertinent of me to try to change him," she suggests.
This meekness extends to the troubling films Gainsbourg made with their daughter, the actress Charlotte. Charlotte Forever, a home movie of sorts, and Lemon Incest, a record and video, applied some of the atmosphere of Je t'Aime to father and daughter. Gainsbourg's fans saw these films as further evidence of his taboo-breaking provocation, though it is hard to watch them now - Gainsbourg and his 12-year-old daughter dancing half undressed, he clutching her chin with a leather gloved hand, or entwined in a bed with silk sheets - without considerable unease. Was Birkin disturbed by them?
"No, I was the one who persuaded her to do it, you see," she says, with her spry innocence. "Therefore I felt responsible for the pain she felt in doing it."
But why did she want to put her daughter through that pain?