It may not be the dress Princess Diana wore on the day of her royal wedding, but the duplicate gown waiting in the wings as a back-up is close to enough to history to be valued at around 50,000 British pounds by Cooper Owen, which will make the piece available at an upcoming auction at the Proud Gallery Camden in London. The dress, tried on by Diana on the morning of the wedding according to Cooper Owen, will go under the hammer with 200 other various cultural artefacts owned, worn, signed or produced by legends of music, film and history. Creative director of Cooper Owen, Louise B. Cooper, said the spare dress was commissioned by Madame Tussaud's as a spare frock in case the original was damaged. The gown was still worn by Diana in public for all the world to see - at Madame Tussaud's waxwork recreation of the wedding. The dress is just one of several costumes donated by Madame Tussaud's to Cooper Owen, including a suit of Winston Churchill's and a Queen Victoria black silk shirt. "This dress is the dress that kind of slipped through the net," said Cooper of Diane Spencer's back-up dress. "Anything that has to do with Diana has been completely controlled in every way possible and this dress is not controlled, which is why it's going out to public auction and that's why it's so special," she added. While the dress, one of several worn by Princess Di on offer, is considered the star attraction of the auction, it won't necessarily be the most expensive item. The original art design for what became one of the most recognisable icons in pop culture is valued at around 750,000 British pounds - the Rolling Stones' "tongue logo". "As soon as anybody takes a look at this logo they know what it's about, what it stands for," said Cooper of the logo. "It's kind of like part of the English heritage of music and so this is why this piece is very valuable and of course it's the original artwork," she said. A tracksuit worn by music legend John Lennon is also expected to draw a lot of attention. "You don't come across these things everyday of the week, I mean fortunately because we're in this business we've managed to acquire top notch A-one grade substance and historical pieces," she said. The cultural relics will be auctioned on December 7.