Filming has started on a movie about a group of Women's Institute (WI) members who started a new trend by posing naked for a charity calendar.

The bare charms of the 11 ladies from the Rylstone WI, in North Yorkshire, proved highly successful with the calendar selling 80,000 copies and raising �500,000 for leukaemia research.

Now their story is being transferred to the silver screen with Helen Mirren, Julie Walters and Penelope Wilton starring in the movie.

Filming on location started in the Yorkshire Dales village of Burnstall, near Bolton Abbey on Monday and is due to last for a month before crews move to London and Los Angeles.

The film follows the calendar's creation

Dozens of charity organisations across the UK and the world have followed the WI's lead since the ladies stripped for the cameras four years ago.

The 12 pictures in the original calendar involved women posing naked in the kitchen with their modesty being maintained by judiciously placed utensils and tableware.

The ages of the models ranged from 45 to 60 - they were all members of the WI branch near Skipton.

The plot of the film has been fictionalised but follows the true story of how the idea was formed after the husband of one of the women died from cancer.

The film tells the tale of how the project went far beyond the group's original expectations.

A spokeswoman for the production company, Harbour Pictures, said: "The story moves from Yorkshire to London to Hollywood.

"A tale unfolds of grit, determination, celebrity, of life in the spotlight and the enduring power of love and friendship."

The movie, which is being distributed by the American distributors Buena Vista, is due for release next year.