"Look," Ralph Lauren says, "I’m in the fashion business, but I’m not in the fashion business." We are sitting by a king-size coffee table in his souvenir-strewn office as the impatient honks of yellow cabs echo faintly up from the New York street below. Alarm bells are ringing, too. What on earth is this Bronx-born billionaire personification of one of the world’s biggest fashion brands on about? Even without a speck of due diligence I’d know that after 46 years Ralph Lauren is America’s alpha-designer: 500-and-something shops in 80 countries, 23,000 employees, 15 (at my last count) separate sub-brands, revenues of $6.9 billion last year alone – and that mallet-swinging Polo player logo, for heaven’s sake. If anybody is "in" the fashion business, then surely it is this diminutive (5ft 6in, according to Vogue) but wiry 74-year-old.  Lauren expands. "What I think is cool is the expression of yourself. That’s what’s cool. Take you, if you’d walked in today wearing some 'outfit' then you wouldn’t look like you. But your dark coat, your scarf around your neck, your shirt – you look like a writer. You look like you. You’re classical but you’re cool. And you’re in the fashion business too. Your clothes are your statement about who you are. And I’m sure you thought it, right?"  Whoa, Ralph Lauren is interviewing me. And trowelling on the flattery as he does it. But he’s also illustrating the idiosyncrasy that makes Lauren so appealing to millions of people who don’t give two hoots about the cult of fashion. Where other designers try to impose an aesthetic on the wearer, Lauren indulges his fantasies, observes his audience then provides them with the tools to share the fantasy. When it comes to mustering a palette of reference he is highly promiscuous: Navajo print and prairie cowboy denim, aviation, safari, field sports, flappers, Tsarist Russia and the all-important Ralph Lauren trope, preppiness, are just a few of the themes he has mined over the decades. "What I do is make movies with my clothes. Movies via fashion."  Today, Lauren has chosen to come to the office he could comfortably have retired from a decade ago dressed in a melange of hiker, biker and cowboy: below a pale-purple down jacket he is sporting some fringed grey leather cowboy trousers and a pair of battered biker boots with a touch of tassel to them. This is not a uniform, though; he has happily appeared in public wearing head-to-toe Lauren-tailored tweed, matinee idol tuxedo jackets (teamed with jeans) and even a sarong. "I live different lives," he says, "but my product and myself, it’s the same thing… Anti-fashion fashion, whatever you want to call it, but something that’s meant to be timeless. Watch Cary Grant in To Catch a Thief tomorrow, next year, whenever – you would still want to be him at the end of it. And a woman will want to be Grace Kelly. That’s timeless."  Because so much of his currency depends on igniting fantasy, Lauren has never overly worried about reality. When he designed his first hit "safari" collection in 1983 he had never been to Africa – in fact he still hasn’t. As he learnt when he first came to England, reality can be a disappointment. Growing up in the Bronx in the 1950s he developed a fondness for the Anglo-influenced preppiness of Brooks Brothers, where he eventually worked. He wore a lot of tweed jackets – on the days when he wasn’t wearing army surplus. "So the first time I went to England [in the 1970s] I was upset. I thought I would see guys with moustaches in hacking jackets. Instead there were Italian suits everywhere and funny clothes in the windows. It was shocking. They thought the Italian stuff was better than what they had been wearing before. So I tried to bring back a lot of the clothes that people thought were old-fashioned and overlooked."  Now Ralph Lauren is thinking of England again, and not just the idealised vision he has become hooked on, Downton Abbey. "It is one of my great pleasures to watch that show. It is so beautiful. The writing is spectacular, the sets are fantastic and the clothes amazing. It’s like, 'Thank you, God, for this!'"  This month Lauren will land in London "for the first time in a long time" to attend a dinner for the Royal Marsden Hospital. It would be poor form to press Lauren for details – philanthropy is its own reward – yet it is fair to assume that the Marsden may be in line for some good news: Forbes magazine ranks Lauren as the 195th wealthiest person in the world, with an estimated $7 billion knocking about in his current account. And cancer care is a long-standing Lauren philanthropic focus. As well as endowing a research centre at Georgetown University in Washington, DC, and donating to American cancer care units, Lauren established one. It was set up 11 years ago in Harlem, after Lauren learnt of the low rates of diagnosis there, particularly among African Americans.  He first became involved, he says, when Nina Hyde, a journalist friend of his at the Washington Post, told him she had been diagnosed with breast cancer. "I’d had a brain tumour just before I met her, and I felt a very strong connection." Lauren’s benign tumour was removed by surgery in April 1987, a few months after its detection. "We started Fashion Targets Breast Cancer in America," he continues. "And for some reason I thought I was going to be able to save her. Because I couldn’t believe that this woman, this alive woman that I was talking to was not going to be here. But she passed away."  It was during this early period of his cancer charity work that he met Diana, Princess of Wales – who was then the president of the Royal Marsden just as her elder son is now. Lauren has met many of his heroes down the years, and proudly escorts me to the en suite bathroom of his office where some of his most cherished trophies are hung: signed pictures from Frank Sinatra (complimenting Lauren on his "smashing" Polo ties), Audrey Hepburn, Gregory Peck and his all-time masculine idol, Cary Grant. Infinitely more respectfully, however, his picture with the Princess sits in a prime spot behind his desk.  "Time goes so fast I can’t even remember when I first met her. But it was during her troubled times, when she was coming to New York. We did this event for breast cancer. Later she presented me with an award in Washington. Once we met accidentally on a plane going to England and had a good conversation. And when I was in London we met at the Connaught for coffee. She had her lady-in-waiting with her, and I had my son with me. We were friendly in a nice way. And she was always shopping for Polo for her kids."  This uptown office, peppered with pictures of princesses and movie stars, is mere miles from the Bronx of Lauren’s extrovert, tweed-wearing youth, but the gulf between them is enormous. "It was a pretty tough neighbourhood. There was this area, Parkway, near all the schools, where we used to sit. Some guys liked what I wore and some didn’t. But I was just an individual, and a good athlete, so no one said anything to me. Anyway it wasn’t about the guys, it was about the girls."  Lauren’s mother, Fraydl, and father, Frank, had emigrated from Belarus. "My father, people say he was a house painter, but he wasn’t. He painted houses when he couldn’t get a job. But he was an artist. Life wasn’t easy with four children so he did what he had to do." Still, the family spent its summers in their small country place in Monticello, outside the city."It wasn’t much but I loved it," Lauren says. As well as sport and cinema, Lauren was always interested in clothes. He keenly recalls staring yearningly through a shop window at a pair of blue suede shoes when he was knee-high to a grasshopper. "Those blue suede shoes are every pair of shoes I ever desired."  After college, a stint at Brooks Brothers and time in the US Army Lauren went to work in 1964 as a tie salesman. Thinking back, Lauren is in full flow. "I had no credentials but I was dressed well. With my last money I’d bought some clothes from Brooks Brothers. And I sold those ties. There was this Englishman, I remember…" He pauses. "He used to come over from this company called, Vanners and Fennell? I don’t remember, it’s starting to slip away. [He remembered correctly, though.] Anyway, I loved the way he looked. He used to wear this beautiful scarf, very casually thrown away. He gave me that scarf and I still have it today."  Lauren’s success as a salesman and his observation that the Mod movement had hit a wall in America inspired him to think he could design some ties for himself that might just fill a niche. "So I asked the company if I could. They said, 'The world’s not ready for you, Ralph!'" Lauren left, found the manufacturer for the then très snob brand Sulka, and produced some three-and-a-half-inch-wide ties under the then-inconsequential brand name Polo. "I liked sports. Cricket was a name I liked, and rugby, which I use now. But I couldn’t call it baseball or basketball." Lauren’s ties, launched in 1967, took off. Soon he found a shirtmaker who could produce the collars he thought would best complement their shape. And then a suit manufacturer to complement the shirts. That suit manufacturer lent him $50,000 to start his company, and so Lauren has expanded ever since, mushrooming slowly from one collection to another.  In 1971, the year after being named America’s best menswear designer, Lauren produced his first collection of women’s clothes, a selection of mannish shirts in whose cuffs debuted the Polo-player logo that has since been embroidered on to tens of millions of garments. The Polo polo shirt, prepwear staple par excellence, was released in 1972. That filmic sensibility was requited by Woody Allen and Francis Ford Coppola when Lauren’s clothes made Diane Keaton look adorable in Annie Hall (1977), and Robert Redford devastatingly dashing in The Great Gatsby (1974). Lauren’s first store, which opened in 1971, was in Beverly Hills, and his designs for those films – and particularly for Keaton – helped define an easy tailored 1970s feminine look that is still influential today.  When Lauren designs it is via the "rig", a minutely detailed physical moodboard collated by Lauren’s team. During a trip to New York a few years ago I saw that season’s rig for RRL (my favourite Lauren collection, inspired by his ranch and all things Western, rugged and worn). There was a vast room with Winchesters and saloon doors on the wall, vintage Johnny Cash shirts by the dozen, cabinets full of belt buckles – a treasury of authentic, vintage raw material to act as a lightning rod for design inspiration. Another room, for his prime Purple tailoring collection, featured a painstakingly – and in retrospect awfully Downton-ish – recreation of an English manor house living room, complete with Persian carpet and fireplace. All of his collections get the same treatment. Which is why, he says, "I hardly ever sit at this desk. I am standing all day long because I work. Going from one office to another, always moving; menswear, womenswear, children’s, wherever I need to be."  Unsurprisingly for a man so immersed in the images he creates, his stores are immersive too. Bond Street, opened in 1984, has an ocean liner-inspired interior, while expats say the Paris flagship on the boulevard St Germain produces the best American food in the city. His ultimate store, though, is a few blocks away at 867 Madison Avenue – the Rhinelander mansion. This magnificent faux-gothic folly of a house was built for, but never inhabited by, a 19th-century heiress and fell into decline before Lauren bought the lease in 1983. He spent millions on its restoration, installed a gleaming wooden staircase modelled on that of the Connaught hotel in London, and turned its interior into the template Ralph Lauren environment, as dense with detail as those rigs.  In 2010 Lauren opened a new building opposite it, a neoclassical chateau made of Indiana limestone to house the women’s collections that complement the men’s in the Rhinelander. In 1997 Lauren took his company to Wall Street, offering 30 million shares at $24 apiece. Long-term investors have since profited: today the share price is around 12 times that, and after years of expansion under his chairmanship the "market capitalisation" of the company is estimated at $14 billion.  So, outside looking in, just as Ralph Lauren once stared at those blue suede shoes, he would seem to inhabit a landscape entirely unclouded by misfortune. Multiple landscapes, in fact. "I live those different lives, and am fortunate enough to have different homes. You wear different clothes in each environment, and live in a different way. Jamaica has the sun, and the beach, and is very colonial. My ranch out west is very cowboy, and that’s another dimension in my life. And the house on the beach in Montauk is very rustic."  These multiple lives have been shared with his wife, Ricky, his sons, Andrew and David, and daughter, Dylan. Campaign-perfect childhood pictures of them on the beach at Montauk, or on the porch of the family ranch in Colorado are all around us. Today Andrew is a film producer, and Dylan runs a four-chain sweetshop called Dylan’s Candy Bar that claims its 7,000-strong selection of lollipops and chocolate to be the largest in the world. Naturally, it sells clothes too. Only 42-year-old David is involved in the company founded by his father. As well as spearheading Lauren’s philanthropic foundation, David is a vice-president of the company and oversees its marketing around the world. He is married to Lauren Bush, the niece of George W. Today the children are a key catalyst for Lauren’s own continued curiosity and drive to innovate. "People are not as old as they were when my parents were old," he says. "My parents’ tastes did not affect me strongly, but with me and my children there is a total connection of life. Age today is not the same thing."  Lauren met his future wife, Ricky Loew-Beer, in 1964, thanks to a sore eye. "I went to the doctor, and there she was. She was the doctor’s assistant, and she kept coming into the room. I thought she was sort of paying attention to me." Lauren insists he was not in the habit of propositioning comely medical professionals: "No, no, no! This was one of those very rare things!" As for Ricky, once Lauren had asked her out on a date, she ran the suggestion by her boss. Entirely unethically, he cast his eye over Lauren’s medical records and family history, then deemed him a safe bet. Ricky and Ralph were married eight months later. Lauren was still at the very earliest stage of his empire-building but that doctor’s intuition proved correct. Today, the marriage is as solid as the Rhinelander and Ricky acts as muse to Ralph as well as family curator; two years ago she published a book of the recipes, photographs and watercolours she created during the children’s formative years summering in the Hamptons. Just as Lauren began by placing himself – and his own fantasised version of himself – at the heart of his work so the family and its six-strong portfolio of exotic properties has become a fashion Camelot-like cipher for the image of his products.  Even unvarnished, then, Lauren’s progress seems charmed. Yet there have, he says, "been lots of shakes along the way. Once or twice I thought I was going to lose my business. And you start to feel pain. That can be good for you, but you still don’t want it to happen." Lauren is a master of crafting idealised images with beautifully made clothes. Set in the context of his painstakingly designed stores these act as a prism for the fantasy lives of his customers. So when the occasional blemish sullies the lens of Lauren’s own image, it rather rankles.  When he was 16, Ralph and his elder brother, Jerry – who is also deeply involved in the company and helps oversee its menswear – elected to change their surname from Lifshitz, which Frank had brought from Belarus. They wanted something easier to live with. "As a kid, when other kids are laughing at your name you don’t want to raise your hand to it in class. You don’t want to have to carry something that is holding you down." Today the snarky sometimes use that name-change to suggest Lauren was airbrushing away his heritage: for a man who is particularly keen on "authenticity", this is annoying. "You know, in those days changing your name wasn’t seen as a denial of where you had come from," he says. "It was because you didn’t want to be made fun of. People came from Europe, and they Americanised their names. And my name had a tough spelling. I don’t know why it was spelt that way – there was a famous artist called Jacques Lifschutz – but anyway, that was the reason."  Another blot came far more recently. When Lauren unveiled his collegiate attire for Team USA at London 2012, most of it came labelled made in china, as at previous Games. This time, though, in an America sensitive to its position in the world and languishing in a sub-prime hangover, it was seized on. "I was battered by politics," Lauren says, "and in politics they suck you up and spit you out again. But I know about manufacturing, I try to make the best products I can, and I try to give my customers value." Lauren’s bemusement is fair enough, when you consider the provenance of most sportswear. "Look at Nike, look at all that stuff. But what happened happened, and I think it will always be a little stigma." For the closing ceremony the athletes wore the same designs, but this time American-made.  Lauren’s assistant curls her neck around the door and says his two o’clock is here – the day’s schedule is a packed one. "You know," he says as we drift towards the exit, "I built my company, and it still has my message. I’m here every day. So when you see the clothes come out you know they are Ralph Lauren…I try to stay tuned so that I don’t become yesterday’s news. You have to move and keep your mind open."  Still, after nearly 50 years in the saddle, doesn’t it all get a bit much? "It does takes its toll," Lauren concedes. "I used to be 6ft 3."
As he prepares for a rare visit to Britain Ralph Lauren talks about a life spent weaving a world of filmic fantasy worth billions of dollars, his frustrations, his love for Downton Abbey and his determination to help cancer charities