The painting was mentioned continually in the show between 1982 and 1992, although was only actually visible in a few episodes.
The auction house has described the 44cm x 34cm painting as “a rare and important piece of British Sitcom history”. It said it was the only known version of the work that survived all nine series of the sitcom.
The painting was a running joke in the sitcom. Set in a small-town café in Nouvion in German-occupied France during the Second World War, the ‘local treasure’ portrait, by fictional painter van Klomp, become a staple prop throughout the series that protagonists were trying to move, steal or hide, and was often concealed in a knackwurst sausage.
The BBC series featured the storyline that forgeries of the painting were made to confuse the Nazis, who were trying to steal it, and numerous copies were made during production, many of which were destroyed or damaged during filming.
It previously belonged to production designer Shaun Moore, who was presented with it by crew as a souvenir. He auctioned the painting for charity in 2007 for around £4000 and it has been in private hands since then.
The full catalogue entry for the lot can be viewed at thesaleroom.com.