Daniel Johnson: There have been lots of books about Hitler and Stalin, but Mao and Stalin are not so often compared. It might be a good-starting point to look at where these two larger-than-life dictators came from.

Simon Sebag Montefiore: Well, Khrushchev, who knew them both quite well, over quite a long period of time, famously said they were utterly identical.

Jung Chang: Yes, and of course Mao learnt a lot from Stalin — basically how he ran China. His methods, even down to little details — these things he learnt from Stalin. He said Stalin was his mentor, and he meant it.