TO the millions of viewers of TV's latest wannabe show, Model Behaviour, Nathan Roberts is a star-struck youngster hoping to hit the big time on the catwalk.

Except he's not. Far from just starting out in modelling, he's worked professionally for FIVE YEARS and is already on the books of 11 agencies - including the one whose bosses will help pick and then promote the show's winners.

Tens of thousands of youngsters from all over Britain auditioned for the series in the belief that professional models were barred.

One of Nathan's former employers - a London-based modelling agency boss - said last night: "I couldn't believe it when I saw him on the set.

"Here was an internationally-known model giving the impression of being someone with no experience who'd just walked in off the streets. It's a disgraceful situation.

"He should be pulled out of the show immediately."

Nathan and his seven fellow finalists are currently living in a waterfront apartment in London's Canary Wharf where the Channel 4 series is being filmed. The boy and the girl winners of the November 15 final will both get a one-year contract with top London-based modelling agency Select - which has two judges on the selection panel - and appear on the cover of GQ or Glamour magazine.

That would not be such a big step for Nathan, 24, as it would for the other finalists. He has already appeared in the Tatler and New Yorker magazines and the French edition of FHM.

He is also signed to agencies in Paris, Cape Town, Barcelona, Tokyo, Miami, New York, Los Angeles, Vienna, Athens and Munich. He is about to star in an ad campaign for a top brand of sweets, has appeared in TV ads in his native South Africa and posed for photographs illustrating a new version of the Kama Sutra book.

At first Freud Communications, the PR firm handling publicity for the show, confirmed professional models were banned from taking part, but later spokeswoman Danielle Robinson had changed her mind. "It really doesn't matter how much experience a contestant has had," she said.

"Some of the contestants have had some experience of modelling. But it would only have been on a small scale and nothing like what the eight finalists are experiencing now."