MY TELEPHONE RINGS. THERE is no warning, no flunky on the line to introduce him. “It’s Philip,” he says casually, the slightly sibilant London accent instantly identifying Philip Green, the retail billionaire with his eye on Marks & Spencer.

I’ve seen and heard a lot from Green lately. Three weeks ago I was invited to spend an afternoon with him at Arcadia, the retail stable he owns and runs, as he inspected new ranges from Topshop, Burton, Miss Selfridge, Dorothy Perkins, Evans and Wallis (he also owns Bhs). This was followed by lunch and an interview back at his offices. What I didn’t know was that he was already planning his £9 million bid for M&S — though there were a few clues, such as the way he bit my head off when I asked what advice he’d give to Roger Holmes, the now ousted chief executive at M&S. “That’s off limits,” he barked.

After the bid was announced, I asked if I could talk to him again — and suddenly here he is on the phone, discussing the deficiencies of the retail giant he wants to buy. “There’s no theatre, it’s not a nice environment, you’ve got to make it easier to shop,” he tells me. “The product is not right, is it? All the clothing needs sorting.”

I ask when he last shopped there himself, wondering if, just occasionally, he might wander from the Arcadia offices on Oxford Street to the Marble Arch store, to buy some socks or underwear. “I don’t do my own shopping but I was in there last month and just thought, I’ve gotta buy this,” he says. What, a cashmere sweater? An Italian suit? No — he is referring to the company. Sunday’s announcement that his friend (and now business rival) Stuart Rose has been made chief executive of Marks & Spencer adds further excitement to his formal proposal, which is likely to be put forward by the end of this week. What happens after that could transform the high street.

According to the British Retail Consortium it is now cheaper than ever to buy clothes; we’ve never had it so good, and Philip Green is the architect of that renaissance. No one has made more money in such a short time. He is a self-made billionaire, the fourth richest man in the UK, and, according to Forbes, the 84th richest in the world. Not bad for a man without a single qualification, who has never worked for anyone but himself. Green says he doesn’t know his worth. “I don’t bother with that,” he tells me. According to the Sunday Times Rich List his assets are worth £3.61 billion. His is the kind of money that buys, as a plaything, a £20 million custom-built Benetti yacht called Lionheart and a 12-seater Gulfstream G550 jet to speed up the commute between London and Monaco, where he lives at the weekend with his wife Tina and children Chloe, 13, and Brandon, 12. He wants to use £1 billion of his family’s money to buy M&S. “I think that shows I’m serious about this proposal,” he says, deadpan.

Green has clear views on why certain high-street retailers fail while other businesses such as his and those he admires, including Zara and Next, thrive. “Businesses need a driver, a leader to make them work,” he says.

He has made all his money from buying and selling both clothing and clothing retailers. He bought Bhs in 2000 for £200 million and turned it into a billion-pound concern within a year. Bhs was a consolation prize; in 1999 he had the finance in place to buy Marks & Spencer, but dropped the bid. In September 2002 he bought Arcadia for £850 million, taking it private and turning Stuart Rose, its chief executive, into a multimillionaire overnight to the tune of £25 million. Arcadia was valued at more than £1 billion a year later when he announced that profits had more than doubled. The term “Green Envy” was coined.

Today Green heads the biggest privately owned retail group in Europe, in control of about 12 per cent of the UK retail landscape. He operates 2,500 stores and employs 40,000 people, and in 2003 his stores generated £3 billion in sales and £252.2 million in profits. Topshop, one of the Arcadia businesses, has become not only the byword for cool design — Kate Moss and Gwyneth Paltrow both shop there — but a money machine too.

His beginnings were less auspicious. Philip Green was born on March 15, 1951, in Croydon, South London, the son of a modestly successful property developer who died when Philip was 12. He was educated at Carmel College, the so-called Jewish Eton in Berkshire, and left school at 16. His first job was buying and selling shoes for a family friend. In 1978, when he was 27, he had his first breakthrough. “A shop called Originelle went bust and someone offered me the deadstock, a lot of Bruce Oldfield and Azagury stuff, for £30,000.” He pauses: “I’ve never told anyone in the press this.

“Anyway. I bought the stuff, dry-cleaned it and was going to sell it on, but I decided to rent a shop on Conduit Street right where Vivienne Westwood is today. Then I was offered 3,000 polo sweaters by Ralph Lauren for £10,000. Back then I honestly had never heard of Ralph Lauren. I sold those sweaters for £10 each; people were buying them by the armful. It was then that I realised, why buy stock when I can buy businesses? ” And he did. Buying each one at a reasonable price, making a success of it and selling it on, achieving vast profits in the process. His first significant success came in 1985 when he purchased Jean Jeanie for £65,000 and sold it six months later for £3 million. Three years later he turned around the menswear retailer Amber Day but things turned sour after he missed a profits forecast. He was ousted in 1992 and vowed never to lead a public company again.

Green is variously described as a retail genius, a brash deal-maker, the takeover king and the man with the Midas touch. He astounded the City with the speed at which he turned Bhs and Arcadia around and paid back much of the £900 million he borrowed to take them private. His talent isn’t for aspirational fashion, but for creating the infrastructure that allows fashion and clothing to be made and sold at the best possible price. He also has a loathing of what he calls “corporate crap”. When he bought Arcadia he discovered that the window displays were being sent by DHL to the stores, while the clothes were being delivered by their own logistics department. Green sent the displays with the clothes and saved £1 million a year. He also has an astonishing memory. One staff member says: “We were buying a range and hung up the new season’ s styles, which were similar to last year’s. He’d say, ‘Bought 20,000, sold 17,000; bought 15,000 sold 14,000’. It’s phenomenal.” Another says: “Things that used to take weeks at Arcadia can now happen in a day with his approval. You can just put in a call and he answers his mobile.”

In today’s lexicon what he does with clothes is called Fast Fashion. Get the clothes designed, manufacture them cheaply abroad and get them in-store in weeks. Sell what cost £10 to make for £20. If it sells, make more. If it doesn’t? The Monday morning “Good, bad and ugly” meetings identify problem items, and sort them. “We’re not cost-cutters,” Green insists. “We’re slick, quick and consistent. We have a very efficient business model. What we do is get a feel for volume and pricing and get the product made in the right places. We have 2,500 suppliers around the world, but we’re adaptable because we know what is going on.”

Green jokes that his is “the second oldest profession” and says that he is still only as good as the frocks in his windows. Discussing “the fluffy stuff” makes him uncomfortable, though. “Fashion is not my skill,” he says. “I have a view, yes, but I might hate something and it might be a winner. What I do know is that Fast Fashion is working for us. All the seasons are rolling into each other, it’s all changed. I can sell ponchos in the summer and bikinis in the winter.”