Juergen asks everybody he likes to pose nude. He’s got quite a collection. It certainly wasn’t my idea, and perhaps I hesitated a little when he asked me – but I said yes. I was used to Juergen; I trusted him. We met a long time ago, at an exhibition in Monte Carlo, and he’d been photographing Andreas [Kronthaler, Westwood’s husband] and me for our advertising campaigns for some time. He’d already done Charlotte Rampling nude, too. He has all kinds of reasons for doing it – he’s just interested in people, and not only the striking and young. I didn’t mind sitting nude for him at all.  He came to our house one evening with his wife, Sadie [Coles, the gallerist], and his little son, Ed. That’s our sofa I’m lying on. I can’t remember whose idea it was for me to get on it: I suppose I just sat down there, thinking that the colours were lovely. The thing about Juergen is that he doesn’t necessarily set anything up. He waits for you to stand where the camera can see you, and then he starts taking pictures. Now and again he might ask you to move slightly for the light, but otherwise he doesn’t give you any direction. You can just tell he’s happy with the photograph, and that’s that.  As a designer, of course, it’s unusual for me to be in front of the camera. When I am, I just try to find out what the photographer wants, and then do my best to get it done. I’ll usually put something into my mind, rather than just standing there blankly – and if they want me to smile, I’ll smile. I’m not particularly interested in photography. I never buy fashion magazines, or even look at them unless it’s to see someone wearing our clothes. I don’t even really consider photography an art form – except in the case of Juergen. He somehow manages to control the medium – photography isn’t like painting, where you can decide how you want someone to look, but Juergen manages it. It must be something to do with where he places you in the picture, and the space he leaves around you.  What’s great about Juergen’s photographs, too, is that they look like me – meaning they actually reflect what I think I look like. And yet they also show me myself in a new way. He’s photographed me again since this series. In the new picture I’m very drawn to these wrinkly old hands with long fingernails. They’re my hands, of course, and yet suddenly they look new and interesting. I don’t know how he does it, but Juergen just seems to get to the essence of you, every time.  When the National Portrait Gallery called and said they wanted my portrait, they asked if I had a painter in mind. I hadn’t: I’d never even considered it. So they asked me to come and look at six painters, and I picked out Johnny. I’m very glad I did. He’s painted me twice now, and he’s become a good friend.  I’d always wondered about the relationship between artist and sitter, and how it might resemble my work as an interviewer. Over the weeks I spent sitting for Johnny – he took photographs first, and then I went in to his studio for around eight sittings – I found many parallels. Nobody likes being scrutinised, warts and all, but that’s what television does – and that’s what a painter does, too. We used to laugh about it. He’d be there making eye contact, or trying to jolly me along with a smile on a grumpy morning – all those things you do as an interviewer to settle somebody into a foreign environment – and I’d say: “I know exactly what you’re doing.”  We’d meet in the morning, around 10, and work until we were hungry – an hour and a half, maybe, or two hours. There are some marvellous paintings in his studio, including a very rude one he did of George Bush, and lots of photos of a nude Sienna Miller: it was a very comfortable and inspiring environment. Johnny would talk a lot, leaning forward – it felt like a conversation, not a one-man show. He’s a very engaging man: funny and well-read. After our morning session, we’d go and have a splendid lunch at louche places like the Chelsea Arts Club and Soho House.  The relationship between artist and sitter is a very strange, very close one. We didn’t discuss in advance how Johnny would paint me – all we talked about was whether the portrait would be full-length or head and shoulders. It’s the same with interviewing: you wouldn’t sit down before the interview and say, “I want to paint this man opposite me as a war criminal.” You interview people to explore the possibilities of who they are. That’s exactly what Johnny does so well.  I like the second portrait Johnny painted of me more than this one – I look more relaxed, probably because I knew Johnny better by then. In this one, I’m regarding Johnny with a rather fatherly eye. Looking at your own portrait is strange and intimate; it’s as somebody else sees you. You think, “Is that how I really look?” But the more I looked at this portrait, the more I saw things I recognise in myself. And when Mary, my wife, came to the studio, she stopped dead. “Oh my God,” she said. I thought she was going to say it looked awful. But then she said:“That’s wonderful.”  It was a really quick shoot. We did it at the makeup artist’s house – it was just her, Mary and me. No fuss, no stylist: all really low-key. The look was very much a collaboration. Mary and I emailed beforehand; she asked if I had any ideas, and I said: “I want to look like Brigitte Bardot.” She wrote back: “OK, see you then, Brigitte!” And that was that: I was going to be blond for the day.  I can’t remember whose idea it was for me to be naked. I’ve never felt weird about that – I think it’s because I grew up one of four girls in a house with just one bathroom, so as a kid it was always impossible not to change in front of somebody. And the great thing about Mary as a photographer is that she makes you feel completely comfortable. I’d worked with her a couple of times before this shoot, and I was really struck by how relaxed she was. She takes her work very seriously – that’s what transforms her photographs into true works of art – but she always manages to create a lovely sense of informality. She’s really encouraging: she’ll constantly tell you, as the model, that what you’re doing is amazing. Then all of a sudden you’re just laughing, and forgetting you’re in a photoshoot. Before you know it, she’s finished.  That level of trust between a photographer and a model is a rare thing. Unlike some photographers, Mary isn’t there to control and transform the person sitting for her, but to shine a light on their personality. That’s what I like most about this portrait: it expresses exactly what I was feeling and thinking in that moment, right down to the dirty soles of my feet. Mary liked that: I hardly ever wear shoes or socks, so I think she thought that showing me barefoot was a great way of referencing that aspect of me.  Would I show this photograph to my grandkids? Maybe. I don’t really keep pictures of myself around, and I don’t Google myself: I like to keep my own idea of who I am. But I do love this picture. Like all of Mary’s work, it’s not about perfection. It’s about me being who I am, and Mary showcasing it. So maybe when I’m an old lady I will be there going: “Look at this, old girl! See how great I looked back then?”  Nothing can prepare you for the experience of being enclosed in a full-body cast. For Paul’s series Life Cast I sat for between 12 and 15 of them. I was covered all over in plaster and silicone, and then had to sit for upwards of two hours without moving a muscle. Even my face was covered: I just had two little holes for my nostrils. All I could think about was breathing.  It was incredibly challenging, both physically and psychologically. I’ve done a lot of rock-climbing, hiking and yoga, and none of that comes close. But it was also spiritual. Paul’s studio was very quiet, very serene and meditative. When the casts came off, it was like a birth of some sort. My skin felt different, my perception was different. It was beautiful.  Paul and I had talked a lot about my posing nude: how we would do it, what it would signify. We’d met a few years before, when I auditioned for his film Rebel Dabble Babble [an installation inspired by the film Rebel Without a Cause]. That went well, so he asked me to pose for some sculptures as Snow White. A year later, he suggested the nude pieces.  It was something I had to think hard about. I’m an actor, but I’d never done any nude work. I was curious, but it was also very important to me that I was actively involved in the process. I was interested in subverting the paradigm of the female figure in art, and in nudity from the perspective of honesty: the stripping away of everything external, and allowing whatever is left to come out. Paul was completely open to that.  Seeing yourself as a sculpture gives you an odd perspective: you see yourself in a way you’re never able to from a photograph, a mirror, or a film. When I first saw the figures in such a lifelike material, I felt a kind of time-space collapse. It was very existentially weird. And yes, it’s strange that so many people have seen such an intimate representation of me – but only when I think about it being specifically me. Even my parents loved it – my mother’s an artist, and they’re both very open. The female nude is one of the oldest images in the history of art. When I think of it that way, it just feels like one of the most honest expressions of an image, and of humanity.  Paul McCarthy's sculptures of Elyse Poppers feature in the exhibition The Human Factor: The Figure in Contemporary Sculpture, at the Hayward Gallery, London SE1, until 7 September. See www.southbankcentre.co.uk  I knew of Sam’s reputation, but I didn’t equate it with the girl I saw sitting opposite me one day in the restaurant of the Sunset Marquis hotel in Los Angeles. She came over and introduced herself, and said that she was doing a series of photographs of men crying. I was intrigued. I hate getting my photograph taken – I’ve had an aversion to it since I was a child – but this seemed like a statement about something that is hardly ever addressed in our culture.  Men are not encouraged to cry – it goes back to something primitive and ancient; perhaps it’s to do with going into battle. A few years before Sam approached me, I’d done a film, Polish Wedding, in which my character finds out his wife is unfaithful. There was a choice about whether he would cry. I did two takes – one doing nothing, and the other spontaneously crying. Afterwards, the producer said they were going with the first take. When I asked why, he said: “Because nobody wants to see a man cry on screen.”  After Sam asked me to pose, I asked her when she wanted to do it. She said: “Now.” We went upstairs to one of the hotel rooms; I sat by the window and within 30 seconds I was crying. I didn’t use any special trick. In fact, one of the reservations I had about the project was that Sam was using actors. I think that was a mistake. People say: “Oh, well, they’re actors – they know how to cry.” But we all have sadness and sorrow in our lives, and thinking about it can produce tears in almost anyone.  I was uneasy afterwards: I felt I shouldn’t have shown that side of myself. I wasn’t doing it as a character – I was doing it as me. It puts you in a very vulnerable position. The whole relationship between sitter and artist is interesting. The sitter has to have a vulnerability and a patience, a willingness to surrender control. And the painter or photographer has to be ruthless. I could sense that ruthlessness in Sam – not in a bad way, but in the sense that she was going to get this photograph, even if she had to wait for hours.  Sam sent me a copy of the photograph. I looked at it once, and then never looked at it again. But I did go, quietly, one afternoon, to see the exhibition of the photographs in New York. I was most interested in watching people’s reactions. I could see them thinking. The best art hits you in the deepest place – the unconscious. That’s what Sam’s work does.
Celebrities from Vivienne Westwood to Gabriel Byrne and Beth Ditto reveal what it's really like to sit for their portrait