It could have fitted snugly on to one of the pair's classic 1970s albums - I Want to See The Bright Lights Tonight, perhaps, or Pour Down Like Silver.
In those days Thompson was part of a group of musicians who left an indelible imprint on the landscape of British folk and roots music. As well as her first husband, whom she met in 1969 while he was still the guitarist in Fairport Convention, she was close friends with Nick Drake, John Renbourn and Sandy Denny, was fleetingly engaged to Joe Boyd, and even more briefly shared a flat with American troubadour Tim Buckley.
Another good pal was John Martyn, whom she had known since they were teenage tearaways frequenting the local folk clubs.
Although she was born in London, Thompson spent her formative years in the south side of Glasgow, her mother's home city. Her brother is the Scottish actor Brian Pettifer and, despite living in England for the best part of 50 years, she says: "I still regard Glasgow as home."
As if to prove the point, on the morning we speak she has been listening to Matt McGinn and the great travelling singer Sheila Stewart.
Glasgow was where she first began performing. "I heard a lot of music there that I liked," she says. "Hamish Imlach, Matt McGinn, and John Martyn, who was already a friend when I was 14. He was Iain McGeachy then.
"We hung out, mostly after school, at a cafe in Calder Street, smoking and playing the jukebox. Later, we would go to folk clubs together and have fun. He always said, 'I'm going to be terribly famous, because I'm fabulous.' I love an attitude like that! He had such confidence from such an early age, whereas I don't know if I did. I always sang and I always wanted to be a singer, and then the folk music thing kicked in when I was about 16."
Thompson and Martyn kept up their friendship after she moved to London in 1966, aged 19, to attend university. Her studies soon fell by the wayside as she fell headlong into the folk scene.
"It was a community," she says. "The amazing thing was that among my friends there was nobody who was even remotely mediocre.
"They were all fantastic. It was strange. Sometimes I would go outside my group and listen to other people, and I would think, 'Well, they're all right, but ...' Sandy, Nick, Richard, John - these people were all extraordinary, and unique. We pushed each other. There was a lot of competition. It's that young thing: competitive and self-absorbed."
Thompson seems far from self-absorbed these days, rarely thinking about, never mind listening to, the wonderful string of albums she made with Richard Thompson between 1972 and 1982. "I don't look back at those records," she says. "Occasionally people send me things and it is nice to hear them, but I don't reflect on them. It is very gratifying that people like them and they still sell. That's the lovely thing."
Following a decade of marriage and music-making - not to mention time spent living in
a Sufi commune - the pair's personal and professional union ended in 1983 when he left shortly before the miserable US tour for Shoot Out The Lights. She was pregnant with their third child Kamila at the time.
In the subsequent 30 years Thompson has raised the children, remarried, sold jewellery - and released only four albums. A clear case of cause and effect?
"Well, when Kami was born I couldn't because Richard had gone and I had just had a baby," she says. "I had to do what I could do. I had three children, I was a single parent, I had a little business. I don't like to say I am a fatalist, but I don't think I was meant to make any more records. I like to keep fingers in lots of pies."
She is rightfully proud of Won't Be Long Now, a fine traditional album haunted by lost loves, spirited drunks and roving sailors. "I love simple and I wanted it to be very folky and plain," she says. Sadly, a long-standing neurological condition that affects her vocal cords prevents her performing it on stage.
"I am even nervous talking," she says. "I am losing breath just talking to you - it's a drag, really. I don't like audiences very much, I am a bit scared."
More gratifying is the fact that, as their collaboration on Won't Be Long Now confirms, her dealings with ex-husband Richard have been amicable for some years. "It has become a good relationship," she says.
"It was nice to work with him, and you can't get a better guitarist, can you? A lot of people say to me, 'Oh, it must be hard to work with Richard.' But it's easy, because I know he is not going to make a mess of it. I am not one for dwelling in the past. It was like having another session player, only a really, really good one. I think of him as part of the family."
It seems apt. More than anything, Won't Be Long Now is a family affair. Recorded in New York at leisurely intervals, alongside old friends such as Dave Swarbrick, Martin Carthy and John Kirkpatrick the album features all three of Thompson's children - daughters Kamila and Muna, and her singer-songwriter son Teddy, with whom she also co-wrote two songs.
"Working with him is a nightmare," she says, laughing. "It is harder with family, you can't tell them when they have hit a bum note; it is easier to say that to people you are not related to. We don't have big barneys, we have ominous silences and then somebody leaves, but it all works out in the end."
Despite these light-hearted grumbles, she is looking forward to recording a Thompson family album later in the year "with all the kids and grandkids. That should be great."
After setting aside her musical career to work and raise her children, she reckons that, at 66, "maybe this is payback time, which is lovely. I didn't do so much back then and my children are helping me do more now. That is a good thought. I gave up a little bit for them and they are giving up a lot for me now."
Won't Be Long Now is released by Topic on Monday