M: A lot of those nursery rhymes are quite dark. Like Ring-A-Ring O'Roses was about the plague, wasn't it?

B: They were invented by children to protect themselves from the fear of a really nasty environment, which it was in the 14, 15 and 1600s. And I think it was the same for me. Inch Worm is my childhood. It wasn't a happy one. Not that it was brutal, but mine were a certain type of British parent: quite cold emotionally and not many hugs. I always craved affection cos of that. Inch Worm gave me comfort and the person singing it sounded like he'd been hurt too. And I'm into that, the artist singing away his pain. A very sad song for me is Sound And Vision. I was trying very hard to drag myself out of an awful period of my life. I was locked in a room in Berlin telling myself I was going to straighten up and not do drugs anymore. I was never going to drink again. Only some of it proved to be the case. It was the first time I knew I was killing myself and time to do something about my physical condition. I had a few scares and thought, "Well, I got through that by the skin of my teeth." Serious haemorrhaging from the nose, passing out... awful stuff.

M: And those songs are still painful to perform?

B: I still enjoy singing them very much. I can separate the songs from their time and place. Especially these days as I have more faith in myself as a singer.

Bowie invites us to hear some tracks from his forthcoming album, Reality. There's a Jonathan Richman cover, Pablo Picasso, the self-explanatory Never Get Old and Nu Killer Star, a great cavorting rocker with grinding guitar, wobbly keyboard and a breathless vocal. Of course, you must tread gingerly here, to avoid what he hates: the platitude of "his best since Low". But, based on this rough mix, this track is a riot.

As Bowie watches from a sofa, the music ignites all those supermodel instincts. Moss drops her shoulder and pouts, then throws her hair back and reaches for the air guitar. Afterwards she runs to Bowie and hugs him like a survivor emerging from a train wreck. He's overwhelmed by her girlish love. "You are a lovely girl," he says. Then he grasps her by both shoulders, looks her squarely in the face and says, "You really are very affectionate."

Bowie really would make an ideal favourite aunt. The tales of bisexual shagging, cross-dressing and drug-taking wouldn't be the usual stuff of rocking chair story-time, but his fond tone is perfect: "Now, Kate, you really must smoke less. Really, my dear, you really should, you do smoke an awful lot."

Bowie has been trying to give up for years. Despite this, as the conversation develops, he reaches across to commandeer the ciggie from Moss's hand. And she certainly does smoke like a chimney. It's partly nerves. It's partly because her new friend asks such awkward questions...

B: Having met you, I have to preface everything by saying I have no idea why anybody ever said you were anorexic...

M: Oh! What? But that was 10 years ago...

B: Still, it was unutterably rude and not at all descriptive of you. You have a fabulous body.

M: Well, I was huge when I was pregnant. She was only 6lb, but I carried it all round the front. And my head turned into a basketball.

B: When we had Lexie, Iman carried it all out front.

M: Yeah, but she's Somalian.

B: You wouldn't know she was pregnant until you looked from the side.

M: I liked being fat for a change. And I had simply the best birth. I had candles and everything. A bottle of Cristal. I had the best time...

B: What are you like, love?!

M: Next question... What's your drug of choice?

B: Now? Coffee. French roast. Then? Bloody hell, girl! I was just getting into harder drugs when you were born [in 1974, the year Bowie released Diamond Dogs]. Ziggy Stardust was actually drug-free apart from the occasional pill: amphetamines, speed.

M: And Acid?

B: No, I was never that kind of person. When we first started doing Ziggy we were really excited and drugs weren't necessary. The first eight months were real fun and then it soured for me. I went to America and got introduced to real drugs and it all went pear-shaped.

M: Because you were doing so many drugs?