Police investigating the disappearance of Madeleine McCann will begin a search of a reservoir in Portugal today.
Divers will look at an area around 30 miles away from where the toddler went missing in the Algarve in 2007.
Suspect 'Christian B' is known to have camped in the area.
Officers have already done a search of the dam, but found nothing.
Simon Harding, a former investigative officer at the Met Police, explains why detectives might be going over old ground:
'Perhaps they want it to be done so that they are 100% satisfied that this area known to be frequented by Christian B has been done satisfactorily.
Where they can hopefully say he's not in that particular area.'