Bob

"Bob" is the Secretary of the Ankh-Morpork League of Temperance and a Black Ribboner. He has unhealthily long fingernails and a bald head. In fact, in the drawings by Paul Kidby he looks just like Nosferatu. Whereas most vampires have inordinately long names and cannot help but continue this tradition even when incognito (such as Ms Jane Mary Betty Ann Pamela von Jones), Bob seems to have really cracked the art of unobtrusive alibis.

However, there is evidence of some correspondance between John "Not-A-Vampire-At-All" Smith the League President and Ms von Jones as to the validity of Bob's claims to vampirism: he sunbathes, buys garlic sausage and you can see his reflection...