Martin Kemp, an emeritus professor at the University of Oxford, is one of the foremost experts on Leonardo Da Vinci. He has recently worked on a translation and collation of the Codex Leicester and he talks Dan through Leonardo's most interesting and prescient ideas. Producer: Peter Curry
Dan Snow is joined by Laura Doan to explore female homosexuality in World War One and Two.
Dan talks to Simon Sebag Montefiore about the letters that changed the course of history.
Every day, ten thousand Americans wrote to Obama. Jeanne Marie Laskas tells their story, and the profound impact that these letters had on the President.
