As an historian, it's important to keep your eyes peeled. Sources are all around us. We're here in Liverpool, where I'm from, and I've often walked past this pub, Doctor Duncan. Now, I know he was a ...

DAN SNOW: Hi, I'm Dan Snow. I'm a historian and I've been going through the BBC's archives looking for material that will help with your understanding of one of history's darkest events ever. The ...