Omnibus theatre, LondonSweet and funny show is based on rumoured vampire sightings in north London in the 1960s and 70s " though it could do with producing a few more goosebumps For a time in the late 1960s and early 70s, the area around Highgate cemetery in north London was believed to be terrorised by a vampire. There were sightings, exorcisms, illicit grave excavations and even some desecrations. At the frenzied h…