I just finished reading This Thing of Darkness, by Harry Thompson and thoroughly enjoyed it. I was surprised to find that Robert Fitzroy was a real person!
I feel somewhat cheated because my main opinion on the book is that it is a wonderful story, full of adventure, beautifully painted vistas, humour, drama and tragedy. So to find the story is based on fact devalues my enjoyment somewhat. Still, it was definitely worth reading except if you followed the above links before reading the book, shame on you!