Seeing the show and buying the poster is commonplace. Watching the play and buying the drawing is a new departure.

But that is what is happening at the National Theatre where actor Ian Kelly produces a full-scale charcoal sketch on stage every night during the play, The Pitmen Painters.

The works are being put on sale in response to demand from audience members. The play by Billy Elliot writer Lee Hall tells the real-life story of a group of miners near Newcastle in the Thirties, who formed an art appreciation class and learned to paint.

Over 15 years, they produced hundreds of paintings of their everyday lives and became famous through exhibitions of their work.

Kelly, 42, plays Robert Lyon, who draws his friend, Oliver Kilbourn, played by Chris Connel.
Each night one of the portraits goes on sale, with a proportion of the proceeds going to the Woodhorn Colliery Museum in Ashington, which houses the permanent collection of the miners' work.

“It seemed the right thing to do,” Kelly said. “If enough money is raised, an art scholarship will be established, too.

“During the first run of the play [last year] I got a bit embarrassed when people would ask at the bar afterwards and I would end up selling and asking for some beer money for the cast.”

Mr Lyon's grandchildren, who are also artists, gave their blessing to the fund-raising idea when the play returned to the National this month.

Kelly said the standard of his works has improved with time but it is still nerve-racking.

“It's utterly, utterly terrifying, particularly as the original from 1941 gets projected 20 feet behind me in the closing moments of the scene.

“The tricky thing is to make it look like something that could be the original,” he said. “But it's a play about art and it seemed absolutely right and pertinent to create something live on stage. I'm very comfortable with it now.”

Hall, who won an Evening Standard Theatre Award for the play, wrote the live drawing scenes into the work because he knew Kelly could draw. Both worked on plays together when at Cambridge University. Some of the real paintings produced by the Ashington Group are currently on show at the National.

And if painting on stage every night was not enough, Kelly has also just published a biography of Casanova. He is giving a talk on the book at the theatre on Wednesday.

The Pitmen Painters previews tonight and tomorrow and runs until 14 April (www.nationaltheatre.org).