Award winning historian, Laurence Rees, answers the key question - How did Auschwitz evolve into a place where over a million people were murdered? Laurence is the author of 'Auschwitz: The Nazis and the 'Final Solution' which won history book of the year at the British Book Awards. It is also the world's bestselling book on the history of the camp. Laurence also wrote and produced the accompanying six part TV series on Auschwitz for BBC TV and PBS.