Marks is the founder and chief executive of French Connection, the trendy high street clothes retailer with the ad campaign that plays teasingly with the four-letter word. More to the point, his company last week turned in an outstanding set of annual results.
While most clothing retailers are happy to have just held on to sales levels, French Connection increased like-for-like sales by 11 per cent in the year to 31 January and Marks claims that this year's figures are even better.
The sudden evaporation of consumer confidence in the second half of last year hit fashion retailers hard. Overstocking led to a rash of discounting and protracted sales. Marks & Spencer turned in an appalling performance and slashed its prices, which had a depressing effect on the entire sector.
Retailer after retailer reported disappointing trading. Arcadia, whose portfolio includes Top Shop, Dorothy Perkins and Principles, reported like-for-likes down 1.9 per cent in January. According to the specialist researchers Retail Intelligence, Kookai said that like-for-like sales were down 11 per cent in the first 43 weeks of 1998-99. Monsoon said like- for-likes were down 8 per cent in the six months to 28 November 1998 and fell by 9 per cent in the proceeding seven weeks.
Yet French Connection is storming ahead. Marks attributes its success to the shops looking right, a strong brand image, sensational advertising and a credible product range.
"The key is to have the right thing in the right place so that the public can get hold of it," Marks says. "If drawstring trousers are hot, our shops are going to be full of them. And that is really one of our skills: we move quite fast. For instance, after the Lennox Lewis fight against Evander Holyfield [which French Connection sponsored] Fcuk Fear T-shirts sold out and we had them back in the shops in four days."
Being able to anticipate what is going to be "hot" and what is not is crucial. "We have a rule in this company: don't look at last year's numbers, look at the next thing that is going to happen. The problem with most retailers is that they are filled with what was rather than what is going to be," he says.
We are now into the territory that drives the denizens of the Square Mile to distraction: the world of design, taste, style and other intangibles. But Marks's confidence in himself is impregnable and he views the City with thinly clad disdain.
"It is all about a sense of style and taste and whether the management of a company has it. There are people who have it, such as Terence Conran, George Davis and Ralph Lauren, people who have been pretty consistent. Hopefully, people will also look at me and say that I've done good things too.
"The problem is that most of the retail business in this country is run by accountants and what have they got to do with a sense of style?"
As Marks owns two-thirds of the company, he is less reliant on the favours of City analysts and accountants, but you get the feeling that his attitude would be much the same even if his circumstances were different. Marks is a maverick who is secure in his identity. If he doesn't agree with the premise of a question, he contradicts you. If he doesn't want to talk about something, he refuses. He is frequently flippant and as fond of curve balls as straight answers. He comes across as if he really couldn't care what you think of him, and whereas with most interviewees this is an act, with this 53-year-old it appears to be genuine.
Nick de Grunwald first met Marks when they were in their teens and aspiring to a career in tennis. (Marks won several junior tournaments.) Some 30 years later they were reintroduced and de Grunwald, who is an independent producer and managing director of Isis, attests that "he hadn't changed at all".
"He is the opposite of the hype and insincerity I encounter in my business. He tells it how it is. He is the same with everybody, including the rich and famous," he says. "I went to his 50th birthday bash where he was surrounded by the glitterati and he treated them just the same as everyone else."
Marks came from a reasonably humble background and has been in fashion all his working life, starting as a "trainee everything" at 17. Unlike many who attain wealth, he has remained unaffected, friends say. He is reluctant to talk about money, but some indication as to his wealth can be gleaned from the fact that he was the second-largest shareholder in the Hard Rock Cafe, which sold for over $400m in 1996. Other entrepreneurial interests include film-making - he was executive producer of Lock, Stock & Two Smoking Barrels - and he is an investor in the Hard Rock Hotel. He is tight-lipped about his other ventures.
Marks, who has fashion in his blood, founded French Connection in 1969. The idea of going it alone was suggested to him by a friend, he says.
"He pointed out that I was working all these stupid hours and asked why I wasn't doing it for myself," Marks says.
His employers made the fatal mistake of offering him a fancy title - director - but with no extra money and no shareholding. It was the impetus he needed to branch out on his own. In the early days he describes himself as a salesman who "had a sense of what was right and what was wrong", who used to "botch a collection together and sell it". A couple of years later he met and fell in love with Nicole Farhi, who worked as a freelance designer and was an enormous influence. Marks and Farhi have a 23-year- old daughter. Their personal relationship finished over a decade ago but they remain joined at the hip in business.
Marks has done just about every job there is to do in the company - from accountancy to packing boxes. He claims not to be very hands-on anymore, allowing other people to run the business.
"I read a few magazines, talk to a few people," he says. "The most important thing is that my role is seen as that of an editor, making sure that nothing goes into our shops that we are not pleased with."
Marks was at pains to give the impression that it is not a one-man show. But those who work with him or for him tell a different story. "He's the boss, no question," says one simply. "If you disagree with him, there is nowhere to go," says another. Disagreeing with him apparently can be a bruising experience.
A hard worker despite his insouciant demeanour, Marks has a busy year ahead of him. The group has announced plans to open 21 new franchises, expand its overseas operations and extend its brands (FCUK and Nicole Farhi) into new fields such as glasses and watches.
He lets slip that a franchise operation for Nicole Farhi will be launched within the next 18 months. Toyota has approached him to launch an FCUK car and Prince Naseem Hamed, the boxer, has approached him for sponsorship.
Meanwhile, he is stepping up his controversial ad campaign, which will be seen on TV in the next two weeks. The ads aren't just in-yer-face confetti. Rather, they reflect the ethos of the company and the man who runs it. The image is carried from window display to annual report, just as that attitude informs every facet of Marks's personality. This man is fcuking confident.