A 75-year-old Russian grandfather has found a new career as a porn star after wandering into a porno audition by mistake.

David Bozdoganov wandered into the Gorodcki production company's studios after mistaking posters for new erotic actors as an advertisement for a muscle man show.

Director for the blue movies, Alexander Plahov says, "We were auditioning for a new film and had a number of couples on stage simulating sex when I saw an old guy standing at the back."

The director set his sights on Bozdoganov, signed him and his intuition was right - all of the movies starring the "Grandpa," have been huge successes.