"I think women today want to look good, they don't want to look young. They want to feel good, they don't want to behave like a teenager necessarily. My ambition has been to navigate this phase of my life with grace and I feel like I'm doing that. I see my priorities changing. I realise that this is a period where you can either go with it or it can be quite difficult."
Can you imagine, she asks, what it would be like for someone who has spent their life in the public eye, to realise suddenly that they don't look the same as when they were 20? "It could be really uncomfortable."
But Macpherson is, she says, at ease. "I feel better now than I've ever felt. I look at pictures of myself when I was younger and I think, 'God, I was so gorgeous there, but I didn't feel it'. Or, 'Wow, I look so much better now'. I was such a dork and I can see insecurity written all over my face, trying to be something I wasn't - even though at the time I thought I was cool."
Born in Sydney, Macpherson had what she describes as an easy, simple childhood. She swam every morning at 5.30am, played netball and lists debating as one of her "greatest" school achievements.
Her parents separated when she was 10 and she moved between her father and mother.
He was a sound engineer who started a shop in his garage and expanded into a chain of stores; she was a nurse, among other things, and remarried a lawyer.
Macpherson can trace herself through her "three" parents. "My step-father taught me commitment, discipline, respect for the world and for difference of opinion. He taught me the importance of education. The things I learned through school have supported me all my life: methodical preparation; making lists. If I put the work in, usually the by-product is a great result."
Her mother taught her flexibility. "She went where her heart was. Do what you love, love what you do. And then my dad was really savvy and entrepreneurial, he thought outside the box. He was a bit of a rebel and a hard worker."
After winning a place to study law at a Sydney university - which one she can't remember - Macpherson deferred and went to model in America. And that was that.
"I just never came home," she says, and laughs. She launched a career in fashion and was married to her first husband, a photographer, at 21. She adorned the much-coveted cover of Sports Illustrated a record five times - hence "The Body" - and, in 1986, Time magazine put her on its cover.
But Macpherson wanted more. Rather than allowing magazines to make money out of her image, she began to make calendars herself. "I thought, 'Why am I doing a calendar for Sports Illustrated? Everybody seems to like the pictures, why don't I just make my own?'"
So she did. In 1989, when New Zealand company Bendon approached her to help it break into the Australian market, she cut herself in on the deal and created what would become Elle Macpherson Intimates. "I made about £20,000 for the year. And then we just grew and grew."
Elle Macpherson at 50 is a very different woman to the supermodel in her 20s. There was the party lifestyle for a start. "I have done it all. I'm a girl from the 80s - what do you think?! I went to Studio 54 and I met Michael Jackson, Andy Warhol and Diana Ross, and I hung out in that scene. It was very hedonistic and there was the rise of the supermodel and the rise of Wall St and it was very potent and intoxifying and fast-paced and exciting.
I was a part of that movement and really indulged and enjoyed. And I was there, 100 per cent." Drugs and booze? She laughs. "Not for the last 11 years."
Today, Macpherson seems a devoted mother. She mentions her elder son's upcoming GCSEs three times, and clears her diary for cricket on Monday and Wednesday afternoons.
She is rigorously organised, although she doesn't make as many lists as she did. "I'm streamlining my life. Before it was like I was in list fog. But there's a lot to be said for making lists and the satisfaction of ticking them off."
Each area of her life is carefully choreographed. "I like to get my nails done because grooming is important to me, and I use my hands a lot. I get them done maybe twice a month and I schedule my nail appointment the same way I schedule a conference call. It has the same importance."
Macpherson used to host a lot of dinner parties but now she rarely socialises during the week. "The kids don't go to bed until 9pm or 10pm, and I don't like to go out before they are in bed. And that's okay."
She separated from Arpad Busson, the multimillionaire father of her two sons, in 2005, and last year married billionaire Jeffrey Soffer. He lives in Florida and Macpherson hopes to move there from London. "I have three beautiful stepchildren and two children, and I married the man I love."
Macpherson is now promoting an "alkalising" food supplement she helped develop with a London nutritionist whom she met in her late 40s, when she wasn't feeling her best.
"I was getting jet-lagged, my skin was really dry, I was not feeling motivated and I couldn't sleep at night. I started putting weight on around my waist, which was unusual for me."
Her supplement is, she says with no hint of irony, a "sort of a gift to other people". She now feels nourished on a "cellular level", but concedes that "healthy diet, exercise, love, lots of water, having a laugh" are also important.
I ask her how she keeps so fit. "Don't obsess. Keep it simple. Have fun. Do sport."
She says she walks, runs and works out at the gym. Whatever happens, she does 45 minutes "of something" a day. It could be acupuncture, stretch, yoga or weights. "Or going for a walk in the park."
The fashion industry has been kind to Macpherson, so I'm not surprised when she sings its praises. "It has supported me for 30 years and I'm in a business made by women for women. I find that incredibly supportive, inspiring and profound to some extent, because there are so many people who are employed in the fashion and beauty world and I feel that people are able to use fashion as a way of expressing themselves."
But when I ask about skinny models, she surprises me. "I think you've got better questions than that one." Really? "Yeah." Why? "I think that's just one of those criticisms that don't have a lot of merit or meaning. Jockeys are very small. And? Football players are really big. And? You have specialised body types for particular jobs."
During the interview I've found myself searching for signs of ageing. I cannot resist asking whether this unusual 50-year-old has had any work done.
"On my house?" she replies and laughs. "It's not really my thing. Quite clearly. Look at this face, it's very natural."
Before we part, I ask for her biggest quality and fault. There's a long pause. "I can't think of a witty answer and it needs one." She laughs again. "I don't want to be too earnest."
