A former detective who has been involved in major missing person cases believes the disappearance of Madeleine McCann will never be solved.
Mark Williams-Thomas, 49, says after years of investigations, McCann's disappearance is "unsolvable" due to vital missing CCTV footage.
In his new book Hunting Killers, Williams-Thomas says a crucial CCTV camera was turned off at the time she vanished, allowing her kidnapper to go undetected.
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"The abduction of Madeleine McCann is one I'd put into the unsolvable category.
"I believe Madeleine was the victim of an opportunistic criminal whose act was random – she wandered out of the apartment and into the path of this person.
"The case hasn't been solved simply because a crucial CCTV camera was turned off, meaning that whoever took Madeleine was not identifiable at the scene."
Despite desperately wanting answers, he says statistics show Maddie's case will likely never be solved.
"The sad reality is, this far on, the likelihood of Madeleine being alive now is incredibly slim.
"Unfortunately, in almost every case of stranger child abduction, within the space of 24 hours the child is dead."
Maddie, who was 3 at the time, vanished during a family holiday in Praia da Luz, Portugal, in May 2007.
The young girl was left alone with her younger twin siblings in their room while their parents Kate and Gerry McCann were having dinner in a nearby tapas restaurant with friends.
The McCanns are clinging to hope their eldest child could still be alive.
Maddie would now be 16.