Cornelius Gurlitt's apartment held around 1,400 pictures from great Modernist artists, from Picasso to Matisse, Renoir, Otto Dix and Oskar Kokoschka. Now experts and the authorities have the task of piecing together who may have owned which picture, after it emerged that Gurlitt's father, Hildebrand, an art dealer had played a key role in the Nazi's attempt to round up what they called "degenerate" art. It has been reported that Hildebrand Gurlitt declared that the pictures were destroyed during a bombing raid, but his son seems to have lived from the proceeds of gradually selling some of his treasures over the years. Julian Radcliffe is the head of the Art Loss Register, a not for profit organization in London which was set up to trace lost art all over the world. He told Gabriel Borrud about the process of being an "art detective".