A 43-year-old German prisoner who travelled around Portugal in a camper van is now the focus of Scotland Yard's investigation into the disappearance of Madeleine McCann 13 years ago.
Police believe he was in the area of Praia da Luz where the little girl, then aged three, was last seen in May 2007. They are appealing for information about the van and the suspect's other vehicle, a Jaguar. The man transferred it to someone else's name the day after she vanished.
"Someone out there knows a lot more than they're letting on," said DCI Mark Cranwell, who is leading the Met inquiry.
Madeleine went missing from an apartment on a Portuguese holiday resort on the evening of 3 May 2007, while her parents were with friends at a nearby tapas bar. The most recent Met Police investigation, which began in 2011, has cost more than £11m.
The force said it remained a "missing persons" investigation because it doesn't have "definitive evidence" as to whether Madeleine is alive or not. Scotland Yard said the German authorities had taken the lead on this aspect of the case because the German suspect was in custody in their country.
Detectives said the suspect, who is not being named, was in jail for an "unrelated matter" and had "previous convictions", but they declined to supply more details.
An appeal on German television was broadcast this evening at 19:15 BST. DCI Cranwell said the prisoner, then aged 30, frequented the Algarve between 1995 and 2007, staying for "days upon end" in his camper van and living a "transient lifestyle".
He was in the Praia de Luz area where the McCann family was staying when she disappeared and received a phone call at 7.32pm, which ended at 8.02pm. Police have released details of the suspect's phone number and the number he dialled saying any information about them could be "critical" to the inquiry. They also want the person who called the suspect to come forward.
"They're a key witness and we urge them to get in touch," said DCI Cranwell. "Some people will know the man we're describing today... you may be aware of some of the things he's done," he said. "He may have confided in you about the disappearance of Madeleine.
"More than 13 years have passed and your loyalties may have changed," he added.
Police said the suspect was one of 600 people that detectives on the inquiry, known as Operation Grange, originally looked at, though he had not been a suspect. After an appeal in 2017, "significant" fresh information about him was provided. Since then, Met detectives have carried out "extensive inquiries" in Portugal and Germany in order to gather more details about him.
Scotland Yard said they were trying to "prove or disprove" his involvement in the case and retained an "open mind".
The Madeleine McCann case: a timeline
3 May 2007: Alarm is raised after Madeleine is found to be missing
September 2007: Kate and Gerry McCann are made "arguidos" - formal suspects - in their daughter's disappearance
July 2008: Portuguese police halt their investigation and lift the "arguido" status of the McCanns and another man, Robert Murat
May 2011: Prime Minister David Cameron asks the Metropolitan Police to help investigate. A two-year review follows
March 2012: Portuguese police launch a review of the original investigation
July 2013: Scotland Yard says it has "new evidence and new witnesses" in the case and opens a formal investigation into Madeleine's disappearance
October 2013: Detectives in Portugal reopen the investigation, citing "new lines of inquiry"
January 2014: British detectives fly to Portugal amid claims they are planning to make arrests
December 2014: Detectives question 11 people who it was thought may have information on the case
September 2015: The British government discloses that the investigation has cost more than £10m
February 2017: Portugal's Supreme Court dismisses a long-running libel case against Goncalo Amaral, former head of the local police investigation, ruling that his book, which alleged the McCanns disposed of Madeleine's body, is protected by freedom of expression laws
April 2017: The only four official suspects investigated by police are ruled out of the investigation but senior officers say they are pursuing a "significant line of inquiry"
November 2018: An extra £150,000 is granted to continue the investigation. It is the latest in a series of six-month extensions which take the cost of Operation Grange to an estimated £11.75m
March 2019: Netflix screens an eight-part documentary about Madeleine's disappearance. Her parents, who did not participate in the film, feel it could "potentially hinder" the police investigation
June 2019: The UK government says it will fund the Met Police inquiry, which began in 2011, until March 2020
June 2020: Police reveal that a 43-year-old German prisoner has been identified as a suspect in Madeleine's disappearance