In a fly on the wall report, Scotland Yard agreed that a BBC team could shadow the work of the Paedophile Unit, part of the Metropolitan Police, part of the Serious Crime Group of the Metropolitan Police. Here is the compelling story and disturbing detail behind the BBC series. Bob Long has teamed up with DCI Bob McLachlan, Head of the Paedophile Unit, to write a book which should be of interest to anyone who has any contact with children. DCI MacLachlan's expert witness describes the subtle work of the police in catching paedophiles, giving guidelines for parents and child carers to minimize the risks.