Five years ago, Madeleine McCann disappeared from a holiday
apartment in the Algarve, Portugal. Why has the little girl, aged
three when she went missing, never been found? Her parents are
adamant that she was abducted, but frustrated at being treated with
suspicion by Portuguese police, they persuaded Prime Minister David
Cameron to order a fresh review. Is this new investigation by a top
unit of the Metropolitan Police the last hope of discovering what
happened? For the first time, the senior UK investigator speaks to
Panorama and explains why he believes he has the "best opportunity"
yet to help solve the mystery of Madeleine McCann.