Assistants to the curator add the finishing touches to the displays of postcards at the Royal College of Art's annual 'Secret' art exhibition in Battersea, south London March 11, 2015. Postcard sized artworks are sold at 55 GB pounds ($83) each to raise money for young art students. Some of the pieces are by famous artists, and the secret is that they are signed on the back, so the buyer only knows which artist created the art, after they have purchased it. REUTERS/Peter Nicholls (BRITAIN - Tags: SOCIETY ENTERTAINMENT)