Britain’smostnotoriousserialkiller,DennisNilsen,confessedtokilling15peoplein1983.Overafive-yearperiod,hepickedupvulnerableyoungmen,luredthembacktohishomeandstrangledthem,beforedisposingoftheirbodiesunderthefloorboards.　　Thetruthabouthowandwhyhekilledhasbeenthesubjectofmuchspeculationinbooksanddocumentariesoverthedecade..bbb