Chapter 3: "Historical Roots: The Vampire in the Middle ages", page 45:-
"It is interesting that in the 2005 film 'Kingdom of Heaven', depicting the Crusades and the fight for the Holy Land, a woman who had committed suicide had her head cut off before burial; this practice itself has links with vampirism, as in folklore one way of destroying a vampire was to cut off its head."
Indeed. For obvious reasons, I gave up reading the book at this point. Towards the end of it there is a section about the tragic murder of Sophie Lancaster. What that has to tell us about vampires, I can't imagine.