Scotland Yard is for the first time trawling through a vast log of mobile phone traffic identified in Praia da Luz, in Portugal, at the time of Madeleine'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.
Gerry, who is from Glasgow, and Kate will appear live in the studio during an episode of BBC Crimewatch on October 14, which will also feature a reconstruction and pre-recorded interviews with the couple.
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."
And Scotland Yard has revealed that since launching its own investigation, 41 people of interest have been identified, including 15 UK nationals, up from 38 people of interest including 12 UK nationals established in July.
The Portuguese investigation officially closed but authorities there are backing the Scotland Yard inquiry and officers from both countries will work together in pursuing leads.
The McCanns are currently suing former police chief Goncalo Amaral for libel over claims in the book The Truth Of The Lie.