the 1986 janner file is mentioned in an investigation into an alleged government cover up but its contents remain a mystery .
the home office has refused to comment on the dossier , which could potentially conceal the name of a second person , it is alleged .
last year nspcc boss peter wanless led a review of home office files from 1979 to 1999 and concluded it would be ` impossible ' to unearth this and the other 113 missing files .
it came as it emerged up to 30 people have now reportedly told police they were abused by lord janner that