Madeleine McCann
Madeleine McCannBritish Police

A 43-year-old German man who used to travel around Portugal in a camper van is now the focus of Scotland Yard's investigation into the disappearance of Madeleine McCann 13 years ago, the BBC reports.

Police believe the man, now in jail for a sex crime, was in the area where the girl, then aged three, was last seen.

Police are appealing for witnesses from the general public to come forward, despite the passage of time, and have stated their belief that such witnesses do exist and have declined to give information until now.

Madeleine went missing from her family's holiday apartment while her parents were at a nearby restaurant. Now German police have stated that they are treating the case as a murder inquiry.