Britain’s most notorious serial killer, Dennis Nilsen, confessed to killing ①⑤ people in ①⑨⑧③. Over a five-year period, he picked up vulnerable young men, lured them back to his home and strangled them, before disposing of their bodies under the floorboards.Britain’s most notorious serial killer, Dennis Nilsen, confessed to killing ①⑤ people in ①⑨⑧③. Over a five-year period, he picked up vulnerable young men, lured them back to his home and strangled them, before disposing of their bodies under the floorboards.