How we met: Nicola Green & Elle Macpherson

'At home she walks about in bare feet and sarong trousers like she's at the beach – and that's the person I've got to know and love'

Macpherson, right, says: 'In my relations with people I always look to feel inspired; few people do that - but Nicola does' (Jean Goldsmith)

Nicola Green, 41

A portrait artist, Green (left in picture) has painted subjects from the Pope and the Dalai Lama to Barack Obama. She lives in London with her husband, the Labour MP David Lammy, and their two children

Elle's known as "The Body", and her physical presence was definitely a defining feature when I first met her. I don't want to say it was overwhelming, but she has this strong presence, a beauty that's not just in her face.

A friend introduced us about 10 years ago, at a time when I was at a low point in my life, living a bit Bridget Jones style. But what I had to hold on to was my career as an artist – and Elle and I had that in common : I could see we were both motivated by this sense of vocation, and whatever has happened [in our personal lives] over the years, we've had our careers.

On the surface there are a lot of differences between us: she's got experience in the world of clothes, which was not remotely my subject, and it's given us a different perspective in our lives, but she's also into art .

A year after we met, I was in New York for an exhibition and Elle was working there, so we met up for a pizza. At the time she was taking her proposals for her lingerie line around the US department stores, but every single one said that there was no market for them – that either underwear had to be practical and cheap, or beautiful, but not both. We had a long chat about that and she talked about her understanding of femininity and why all those department stores were wrong. I think they look great; I'm always wearing one of her bras and pants.

Most of my portraits are of powerful men – Barack Obama, the Pope, the Dalai Lama – but that conversation stayed with me; I realised that Elle had, perhaps uniquely, taken her experience of femininity as a model – when she was largely being objectified – and turned that around and made it into global brand for women of all shapes and sizes who now buy her bras. I decided then that I wanted to paint a portrait of her.

We spent the next three years discussing the project and it became collaborative; we went to the National Portrait Gallery together and looked at great portraits of women which manifested femininity and power: Cranach's Venus and Queen Elizabeth I. I made Elle's portrait lifesize, as I think that reflects the feeling I had on the first day we met.

She's always been a few years ahead of me as a mother, with her two boys. I had my second son in 2008, just before I travelled to the US and followed Obama on his first campaign trail, which meant I was leaving a five-month-old and a two-year-old at home. I had no idea how to cope with the relentless jetlag, coming home to be awoken at night by babies, and then make my work in the studio and support my husband while trying to remember to look after myself. But I learnt a lot from Elle, talking about juggling freelance work, relationships, nappies and school runs.

When she's dressed up in high heels, you don't see the down-to-earth straightforward Australian she is. Her sheer Australian-ness has always struck me: at home, she walks about in bare feet and sarong trousers like she's down at the beach – and that's the person I've got to know and love.

Elle Macpherson, 49

After making her modelling debut aged 19, Macpherson went on to grace the cover of every major fashion publication. She has since launched a lingerie line and skincare products, and presented TV shows including 'Britain and Ireland's Next Top Model'. She divides her time between London and Miami, where she lives with property-developer husband Jeffrey Soffer

We met through mutual friends at a function that Nicola was speaking at. I thought she was articulate and intelligent, and we chatted after her talk. I knew she was going through a difficult time, as she had just broken up with someone, and as I had gone through a similar experience, we connected.

Art is important to me in the sense that I've been collecting since I was young. I like lots of British artists, such as Lucian Freud and Tracey Emin, and when I found out she was an artist and doing work around laughter, I was fascinated. I knew she had worked with Obama, and I thought, this is a girl who had vision, so we stayed in touch, and art became our shared passion.

One afternoon after she had come around to my house, she said, "Elle, you have no happy snaps of yourself at home!" I'm photographed all the time, images of me are a business, so in my house I take all the photos. So Nicola suggested doing a portrait of me. Over the next few years we talked about it a lot: I loved how she wanted to tell a story through this portrait, about a definition of femininity; that one doesn't have to wear a power suit to be perceived with inner power. Though there was a possible con to this: she was a friend, what if I didn't like it and I ended up offending her?

Another part of our shared connection was a serendipitous one; a year or so after we met I was sitting in a taxi in New York, with my trusted legal adviser of many years, when I got a call from Nicola excitedly telling me she was now engaged. I was so thrilled, and when I hung up I explained to my adviser how this girlfriend of mine was marrying this young British politician when he got a call too – and it was from David Lammy, telling his friend he'd got engaged to this artist, Nicola Green. It turns out my adviser was David's mentor – he helped put him through law school – and they were already very close.

Nicola is removed from my world perspective as we're in such different [fields], and we experience the world differently; I'm a more feeling person than a seeing person as she is, and she doesn't allow herself to be distracted by life's clutter, as I do. But when we chat it's like a piece of jazz music – we go off on a tangent together.

I love how understated she is about things. I remember one afternoon she was visiting for lunch when she suddenly said, "I have a dinner to go to and I don't know what to wear!" So I asked, "What kind of dinner is it?" And it was for Obama's inauguration, at the White House. So I said, "Right, come upstairs," and we went through my wardrobe. To be honest, I never thought we'd find something that would fit; I'm 6ft tall. But we found this royal-blue satin dress and she put it on and she looked so beautiful and elegant.

In my relations with people I always look to feel inspired; few people do that – but Nicola does. What do I see when I look at her portrait of me? I see wisdom, a mother, a young girl, I see simplicity and strength: all the things, in fact, that I see in her.

'Elle the Body' by Nicola Green will be available to view at the London Art Fair (londonartfair.co.uk) from 15 to 19 January. For more information on prints: flowersgallery.com