Rose Wiley, 80, wins one of Briton's most prestigious art awards - more than 60 years after she started studying at art school.

As an impoverished art student Rose Wylie posed for a painting to illustrate a nationwide advertising campaign for Aero bars aimed at women, with the slogan that this chocolate was "different".

That was more than 60 years ago, but Ms Wylie has now found fame in her own right. The 80-year-old has become the latest winner of the John Moores Prize, one of the most prestigious painting awards in the country.

With her work recently displayed in galleries in Washington, New York and Amsterdam Ms Wylie is not exactly an overnight sensation. It's unlikely many people beyond the art cognoscenti will have heard of her until today.

But the John Moores Prize, presented to her at the Walker Art Gallery in Liverpool on September 19, has finally established Ms Wylie's place among the pantheon of Britain's leading artists.

She said: "My sort of age group don't think about recognition, we just think about getting on with the work. This sudden interest is peculiar and it's certainly unexpected, but it's wonderful."

The prize comes some 60 years after Ms Wylie - who describes herself tongue-in-cheek as "blinking old" - took up her studies at Folkestone and Dover School of Art, where she subsidised her income by working as an artist's model.

The celebrated portrait painter Anthony Devas painted her as one of a series of women for the Aero Girls advertising campaign in the 1950s, and her face appeared on posters, newspaper and television advertisements above the slogan "Different for her, Aero - the milk chocolate that's different!"

The paintings, including the one of Ms Wylie, were only recently rediscovered, gathering dust in boxes of paperwork from the Rowntree chocolate makers, held at the archives of the University of York's Borthwick Institute.

Ms Wylie had almost forgotten the painting, until one of her children told her about a project to track down the models who sat for the series.

She cannot remember how much she was paid for the sitting, but she did not like the result - too 'chocolate box' for her.

Now, of course, Ms Wylie is the one who decides how the subject appears, including Nicole Kidman, the Hollywood superstar, who she painted earlier this year in the guise of a child, after seeing pictures of her at a film premiere.

From the back, Kidman looked as if she didn't have anything on her top half, except for a single black strap. "Only children would dress like that," said Wylie.

She has also painted Chelsea footballer John Terry as King Solomon and her work - described by critics as "exaggeratedly naive" and "quasi-cartoonish" - has something of a following among the A-list.

Puff Daddy, the rapper and music producer, owns a painting by Ms Wylie bought for him by Naomi Campbell in Miami. Another of her paintings shows Richard Branson being interviewed on television, partially hidden by a giant armchair.

Ms Wylie told The Sunday Telegraph she likes to paint the famous because it provides her viewers with a recognisable model.

"When you paint a celebrity people can see how much you've transformed them and how much of their character you've retained or interpreted, in a way that would be harder if it was a member of your family or a friend," she said.

"When I chose to paint John Terry as King Solomon I wanted someone who was instantly recognisable as rich."

After leaving art college Ms Wylie married fellow artist Roy Oxlade, who died in February, aged 85, and gave up painting to raise their family. She picked up her brushes again when she was in her mid-40s and resumed her training, this time at the Royal College of Art, in London.

Four years ago, at the age of 76, Ms Wylie was chosen to represent Britain in the Women to Watch exhibition at the National Museum of Women in the Arts, in Washington DC - for a show exhibiting "up-and-coming artists".

The event, along with a number of other key shows and an interview with Germaine Greer, raised her profile and suddenly she found demand for her paintings.

She said: "It happened when a number of things came together, as is often the case. I'd been painting pretty obsessively for years and there was so much of my work around the house it was getting difficult to know what to do with it.

"Now the process has been reversed and the paintings are going out of the house and it's lovely they are being seen more widely."

The painting for which she won the 25,000 John Moores Prize - whose previous winners include David Hockney and Richard Hamilton - is titled PV Windows and Floorboards and shows figures at a private view in an art gallery.

Ms Wylie says she draws inspiration from the excitement of what she sees around her, whether personal events or in films and newspapers, and says she often tries to draw what would normally be stereotypes from an un-stereotypical viewpoint, something she calls "conceptual projection".

The John Moores Prize, founded in 1957 and part of the Liverpool Biennial arts festival, has no upper age limit, unlike the Turner Prize, which excludes artists over the age of 50.

Sandra Penketh, director of Liverpool's art galleries, said: "Rose's personal story is very exciting. At 80 years old she happens to be double the average age of previous winners.

"Her style is fresh, unpredictable and cutting edge."