"I drew this picture in 1978 when I worked at the Co-op (supermarket)," wrote Greenhalgh in new book "A Forger's Tale," extracts of which appeared in the Sunday Times.

LONDON.- One of Britain's most notorious art forgers has claimed responsibility for what is believed to be a Leonardo Da Vinci masterpiece, saying it was inspired by a supermarket checkout girl, the Sunday Times reported. 

Experts agree that Da Vinci created "La Bella Principessa" in the 15th century, but Shaun Greenhalgh, who has spent time in jail for art forgery, claims he made the chalk and ink drawing when he worked at a supermarket in Bolton, northern England. 

"I drew this picture in 1978 when I worked at the Co-op (supermarket)," wrote Greenhalgh in new book "A Forger's Tale," extracts of which appeared in the Sunday Times. 

"The 'sitter' was based on a girl called Sally who worked on the checkouts," he added. "Despite her humble position, she was a bossy little bugger and very self-important." 

Experts concluded in 2008 that the profile of a blonde-haired woman was a "remarkable drawing by Leonardo", and it has since been exhibited as a da Vinci in Italy and valued at £100 million ($150 million, 142 million euros). 

Greenhalgh, who was arrested in 2006 and jailed for four years and eight month, claims he used an 1587 council document for the canvas and schooldesk lid as the backing. 

While executing the artwork, he turned it 90 degrees clockwise to mimic da Vinci's left-handed style, he wrote. 

However, a laboratory recently released evidence suggesting the chalk pigment was at least 250 years old. 

Greenhalgh claimed he made his own pigments from organic materials of an appropriate age, digging up iron-rich clay. © 1994-2015 Agence France-Presse