Andrew Marr finds out how much faith and science can tell us about identity with Tariq Ramadan and Sir Mark Walport; historian Jonathan Phillips explores the relevance of the Crusades, and curator Kate Bush discusses the search for the next Young British Artist.
Tom Sutcliffe discusses tradition and modernity with musician Nitin Sawhney, drama and wartime plots with writer and director Stephen Poliakoff, progress and conservation with the science historian Harriet Ritvo, and the uses and abuses of scientific ideas with Dennis Sewell.