What happened to Madeleine McCann? How many times has that question been asked in the six years since she disappeared? How many times have you wondered it yourself or asked others?
It is likely only one person really knows the answer, and finding that person is now the focus of a British investigation led by officers from the Metropolitan Police, funded by the Government.
For the last two years they’ve studied all the documents and interviewed witnesses. Some have offered new information.
As a result detectives say there are now 38 people they want to talk to in the hope of finding out what happened. All were in Portugal at the time Madeleine disappeared and now live there, in the UK or in three other European countries. Twelve are British.
Police are understandably cautious but it is a significant development in a case that haunts and endures. They continue to insist that in the absence of any evidence to the contrary they believe she may still be alive.
British officers have now visited Portugal 16 times and are working through more than 30,000 documents.
They have ruled out any involvement of Kate and Gerry McCann or the seven friends who were holidaying with them.
The review has taken in evidence from British officers asked to look into parts of the case, from the Portuguese and from the seven teams of private investigators hired by the McCanns to find their daughter.
For their part the McCanns have welcomed the shift from review to investigation.
The investigation is being done with the full co-operation of the Portuguese.
A number of British officers have been and will be based in Portugal as the investigation continues but their work is fraught with difficulty as a result of working across different countries and different legal jurisdictions.
Madeleine was three-years-old when she vanished from the family’s holiday apartment in the Portuguese resort of Praia De Luz in May 2007. In the years since there have been many reported sightings but no clear lead.
The Portuguese investigation was closed in 2008. Under Portuguese law it could only be re-opened if significant new evidence came to light