I'm sure that Des's widow, children, grandchildren, and great-grandchildren would be quite upset to learn he really died in 1915! I'll have to write and let them know....
Now the serious answer. Yes, Des Cox survived the sinking. He died in September, 2000. I was lucky enough to contact him about eight years before he passed away. Although he remembered nothing of the sinking, being only about 18 months old at the time, he was extremely helpful with information about himself and his mother's experiences, and we kept up quite a lively correspondence until his passing. He took a keen interest in every aspect of the disaster and followed all
Lusitania-related news with great interest.
As for Diana Preston saying that he died, well, that's one of the reasons I can't take the book seriously. That and getting many names wrong. Names are among the most easily verified facts, and if those are incorrect, I can't begin to imagine what else is wrong. I haven't read the book (and don't really plan to until I can find it on the bargain book shelf), and I'm almost afraid to. This just shows that it's not the end-all, definitive book that the publishers claim.
It just proves what I always say -- If it's in a book, don't believe it until you verify it with a reliable source!
Eric Sauder