Peggy Seeger’s face flashes up on my computer screen from her home in Oxford. “Oh, there you are,” she says, then launches into bright, familiar conversation, sounding less like the grande dame of folk music and more like an old friend dropping by for tea. Her hair is short and white; her lipstick and scarf bright pink. Her striking features remain recognisable as those that, more than 60 years ago, inspired one of the most beautiful love songs ever written.

Back in 1957, Seeger was 22 years old and in a relationship with Ewan MacColl, a married Scottish folk singer almost twice her age. That year, he composed The First Time Ever I Saw Her Face in homage to her beauty. Twenty years later, she would become his third wife, but at the time, Seeger says: “We weren’t talking to each other much, because I was living in California, and he was over here, and transatlantic calls were unbelievably expensive.” She laughs. “But I called him on my stepmother’s telephone bill, and he sang it over the phone to me. Such a happy song: it goes from the first kiss to being in bed together.”

Seeger transcribed the song over the phone, and recorded it in a high, sweet fluttering voice, accompanying herself on autoharp. Strikingly lovely though it is, it wasn’t until Roberta Flack made her own darkly sensuous recording of the song in 1972 that it became a modern pop standard. “We were horrified!” says Seeger, laughing. In Flack’s version, “three-quarters of the tune is not the tune that Ewan wrote. We thought it was horrendous. Never mind, the royalties still come in.”

Seeger has had an extraordinary life in music: her 70 solo and collaborative albums, combining traditional songs with her own lyrically intricate compositions, are a landmark in modern folk. But, she suggests, her new album – out next month and called First Farewell – may be her last.

“I’m 85. I have arthritis in my hands. My voice is not what it used to be,” she says. “There’s notes that trouble me. I don’t want to fade out, I want to go out with a bang. I’m proud of this album. It has songs about memory, correlating joy and sorrow, past and present, hello and farewell, it feels like a good note to end on.”