The detective leading the British review into the disappearance of Madeleine McCann has spoken of now having the "best opportunity" of finally solving the mystery of what happened to her.
Detective Chief Inspector Andy Redwood said his inquiry, named Operation Grange, had access to all of the available evidence in one place for the first time.
It will be five years ago next week since the three-year-old went missing from her family's holiday flat in Praia da Luz in the Algarve, as her parents Kate and Gerry McCann dined with friends nearby.
There have been hundreds of possible sightings of her all over the world since she vanished, but so far they have come to nothing.
Mr Redwood told the BBC's Panorama programme that his team of 28 detectives and seven civilian support staff were handling a large number of reports and documents from both Portuguese and British police along with private detectives.
He said: "I am satisfied that the systems and processes that we are bringing to this set of circumstances will give us the best opportunity to find those investigative opportunities that we can then present to our colleagues in Portugal.
"Our initial estimates in terms of the amount of material we are facing is that it will be somewhere in the region of 40,000 pieces of information. There is, ultimately, a process of us turning every single piece of paper over and interpreting and analysing what is contained within them."
Asked by reporter Richard Bilton if Madeleine's disappearance on May 3 2007 could be solved simply by reappraising documentary evidence, he said: "Anything is possible, and clearly, within that material, the answer could lie."
The Metropolitan Police detective is the senior investigator in the inquiry, which was established last May after David Cameron responded to a plea from Madeleine's parents to hold a UK police review of the case. To date the review has cost taxpayers £2 million while officers have made two trips to Spain and visited Portugal four times, most recently last week.
Mr Redwood told the programme: "We are here in terms of seeking to bring closure to the case. That would be the ultimate objective and is our ultimate objective. We are drawing together information from three separate sources. The legal enforcement bodies within Portugal, the UK enforcement agencies of which the police are the main part, and also and unusually the private investigation world which as we know is an element that was used by Mr and Mrs McCann in the search for their daughter."