The interviewer tries not be cynical, but sometimes it is hard. The subject has just finished bemoaning his considerable weight - about the pressure it puts on his ankles,
especially on long trips, and how it is the fault of metabolism and not over-eating - when suddenly he proclaims: “Snacky-poo time”.

A young assistant, Scott, who minutes before had settled into a corner to take notes, jumps up. The hungry man is Peter Arnell, who on this Saturday afternoon is at home in his imposing, top-floor apartment on the southern edges of Manhattan’s Soho. Somewhere, one assumes, there is a kitchen.

True, when the obedient Scott returns, the food gives a convincing impression of healthy. Raw vegetables with dips (not too creamy). And while there is a good crust under those pizzas, Arnell insists they contain no salt.

It is easy to see why others have likened Arnell to Orson Welles. Large men both, in girth and in playfulness. Arnell knows I am distracted by his head which he keeps jerking left to right in the manner of a nervous twitch. Finally, he grabs it with both hands and twists it violently until the realigning of the vertebrae issues a loud, unsettling crack. “I had a car accident,” he offers in explanation.

Large in talent too. At 38 years old, Arnell is one of those New Yorkers who make the city - or at least lower Manhattan - what it is. You don’t meet them often, but it is riveting when you do. He is brash, brilliant, wealthy - he has his own jet and there is more electronic hardware in here than in an average Curry’s - and probably ruthless. (Witness how fast Scott moves.) Moreover, he does something that actually marks the city. His company, the Arnell Group, based in two buildings on fashionable Prince Street, makes images for corporations. It is advertising-plus, not just marketing a product but helping a company create them in the first place. With a staff of 140 in New York, San Francisco and Tokyo, Arnell has had clients running from Banana Republic, to Anne Klein, Bausch & Lomb and Chanel. Most intriguing, however, is his passion for “vertical-surface” advertising: putting a client not just on to billboards but on to the walls of buildings.

You do not have to be especially observant to know that giant advertisements placed on exterior walls, some of them many storeys high, are suddenly the rage in Manhattan and particularly in SoHo. The murals, touting anything from underwear to cigarettes and television channels, are fast becoming a defining feature of the island’s landscape, like skyscrapers, exterior fire escapes in the Cast Iron District and the wooden water towers that sit on so many rooftops. If there is a naked brick that the public can see, it is going to get covered. The ads are always hard to miss. A few are interesting to the eye. Some you might even call art.

Mr. Arnell is more than peripherally involved. Any of the newest and most striking of the new wall-ads out there are his - indeed, he is arguably responsible for their current wave of popularity - and he is also gripped by them intellectually. He has asked the Guggenheim Museum - a client, as it happens - to consider dedicating a whole exhibition to the topic.

If he has a special feeling for the murals, it may be thanks to his background. Brooklyn-born Arnell set out as a trainee architect under the wing of Michael Graves in Princeton. With a fellow trainee, Ted Bickford, he later embarked on a business publishing specialised architecture books. Only later did the pair almost accidentally pick up an advertising contract with the luxury Bergdorf Goodman department store. From there, Arnell progressed to what he is doing now, after parting company from Bickford in 1993.

Before the afternoon light goes, we do a tour of southern Manhattan. We pass by a Coca-Cola mural on West Broadway and Grand so old the paint has all but faded from the brick. Then we visit the Federal Reserve building on Wall Street, where all the money is held. There are no murals here but, with its window grilles and granite-block walls, it still sends a clear message to anyone who looks. And, says Arnell, it is simply: “Fuck off”.

In the late Eighties Arnell executed a single project, the impact of which still has not worn off. Indeed, you will see renditions of it on Big Apple T-shirts and postcards in cheap souvenir joints  around the world, from Bangkok to Ouagadougou. Arnell likes to think that, as an icon of a city, it is to New York what the red double-decker is to London. We are talking just four letters: DKNY. They were, of course, for fashion designer Donna Karan, who had asked Arnell to find some way of giving brand identity to her spin-off business in accessories and cosmetics.

Today, those four letters stare down from three sites around Manhattan. In shades of grey, the initials show an aerial view of Manhattan island, taken by Arnell himself on a seaplane ride down Manhattan with his wife, Sara. Superimposed on the whole thing is a transparent Statue of Liberty.

With the DKNY ads, interest in mega-sized murals was rearoused and the current fad for them began. Nowadays the ad murals come in two forms. Many are indeed frescos, executed with brush and spray gun by artists, some imported from Italy. (They, you might say, are honouring the legacy of their own Michelangelo in the urban age.) A colleague of this correspondent recently parked his car beneath one of Arnell’s creations on a day when it was still a work in progress. He later returned to find his car spattered with paint.

Others, however, are actually gigantic hangings. Thanks to recent advances in giant-scale printing, advertisers can now transpose their images on to huge areas of nylon webbing that are pinned to buildings like rugs. They have the obvious advantage of being easy to take down when their impact wears thin. The frescos, by contrast, risk staying up for as long as the buildings.

Arnell is also behind the most striking of the hangings campaigns, a series of giant webs advertising the electronics products of Samsung attached to buildings on Sixth Avenue in the Chelsea neighbourbood. One is 14 storeys high. Just as he took the photograph for the DKNY image, he also shot the Samsung spots aiming to give an unlikely patina of fashion and sex to such things as laptop computers and camcorders. One tracks the Adonis contours of a bare-chested man with a microwave under his arm. The text reads: “Work out. Stay healthy. Cook your vegetables in a microwave to retain the vitamins.”

His newest offerings, however, are on Houston Street, on the northern edge of the Soho district. They are all for Fila, the French sportswear company. One is actually three-dimensional, featuring a painted alpine mountainscape and a to-scale figure dangling from a rope and dressed, of course, in Fila clothing. Two others are much brasher. In two dimensions they showcase two US sporting stars who endorse Fila: Derek Jeter, a pitcher with the New York Yankees, and Grant Hill, a meteor of the basketball courts.

Some Houston Street residents are getting restive about the murals. Arnell admits that the Jeter and Hill spots have provoked letters of complaint. “They probably ended up being too loud. If you go for bright lights, you end up offending people.” The other problem is that Arnell’s are far from the only murals on Houston Street. Competitors have tattooed whole walls for clients ranging from Beefeater Gin, Ralph Lauren, a brand of vitamin pills and an unpronounceable Russian vodka. Over Christmas there was an Absolut Vodka sign with “Absolut Noël” blindingly spelt out in lights.

Worried that concerns about the intrusiveness of the murals will only mount, Arnell predicts an early crackdown by the city’s politicians. But he blames others for indulging in what he considers “crap” concepts that are either devoid of artistic merit or totally insensitive to the surrounding environment or both. He especially rails at Gap, whose murals are usually nothing more than giant pictures of models in their fashions. “Why are we having these problems today? Because advertisers for the most part are not taking the environment into consideration. They’re not considering the media carefully, and if they’re not considering it, it will die.” He repeatedly contrasts what Gap is doing with its hangings up and down Manhattan with his DKNY mural. “I never got anything but good reaction after the first DKNY, because it was a one-off, not a one thousand-off. It’s part of the fabric of New York. That is a very rare achievement.”

Adopting an uncharacteristically tentative tone, Arnell confides, however, that deep down he wishes he had been able to get off the mural train after the DKNY and Samsung advertisements and possibly the climber too. But when asked if he is prepared now to pack up the brushes and turn down any other clients asking for murals he is conspicuously non-committal. (A Casio watch mural campaign is in the works at the Arnell Group as you read this.)

And he does have one more project that he would dearly like to execute if only Donna Karan would let him. He wants to take that other treasure of lower Manhattan, the little round water towers, and emblazon them with the DKNY initials. Each letter would be applied singly to individual water towers buildings apart from one another. Then, from viewpoints blocks away, we, the public, would See DKNY spelled out across the city skyline. A brilliant idea, typical Arnell? For sure. The ultimate in visual pollution of the city for commercial ends? That, too.