Scotland Yard is for the first time to trawl through a vast log of mobile phone traffic identified in Praia da Luz, in Portugal, at the time of Madeleine McCann's disappearance.
In a process detectives say could be key to discovering what happened to the-then three-year-old, any person who was present in the Algarve town on or around May 3 2007 could receive a phone-call from the Metropolitan Police.
Describing the programme, Assistant Commissioner Mark Rowley, of the Metropolitan Police, said: "It's substantially different. It's not just a bland 'can you help us' appeal, there is some different material and a different understanding to be presented."
More top news
Oliver Letwin MP, who was in charge of Brexit negotiations for two weeks, tells ITV News what he thinks will be easy and what will be hard.
Theresa May's decision to delay green-lighting Hinkley nuclear plant has put noses out of joint. But EDF is confident it will go ahead.
Highs of 23C at best in the afternoon sunshine but feeling cooler in the mornings and the evenings.