Video report by ITV News Correspondent Rebecca Barry
German media have named the new suspect in Madeleine McCann disappearance as Christian B.
The man is 43, and described as white with short blond hair, possibly fair, and about 6ft tall with a slim build.
Police confirmed the new suspect is a child sex offender, although none of his convictions are thought to have any links to the disappearance of three-year-old Madeleine in Portugal in 2007.
She vanished shortly before her fourth birthday and would have turned 17 last month.
German police are treating her disappearance as a murder investigation but the Met’s Operation Grange, launched in 2013, has always considered the case a missing person inquiry.
Hans Christian Wolters, a spokesman for the Braunschweig Public Prosecutor’s Office, said: “We are assuming that the girl is dead."
On Wednesday, Germany’s Federal Criminal Police Office (BKA), told the country’s ZDF television channel made the announcement about the suspect.
Christian Hope from the BKA said German police have not ruled out a sexual motive, but added that the suspect may have broken into an apartment in the Ocean Club complex in Praia da Luz – where Madeleine was on holiday with her parents, Kate and Gerry McCann, and her twin siblings Sean and Amelie – before spontaneously kidnapping her.
The German national is known to have been in and around Praia da Luz on the Algarve coast at the time Madeleine vanished on May 3, 2007.
Clarence Mitchell told ITV News: "They [the McCann family] need to find peace, they need to know what happened and they simply want to know the truth and find whoever was responsible for Madeleine’s disappearance brought to justice."
Mr Mitchell added the Madeleine's parents, Kate and Gerry, welcome the unearthing of a new suspect.
Journalist Clarence Mitchell who has worked closely with the McCann family says they are realistic with the outcome.
The Metropolitan Police are leading the UK-side of the investigation and have launched a joint appeal with the BKA and the Portuguese Policia Judiciaria (PJ), including a £20,000 reward for information leading to the conviction of the person responsible of Madeleine’s disappearance.
The Met’s investigation has identified more than 600 people as being potentially significant and were tipped off about the German national, already known to detectives, following a 2017 appeal 10 years after she went missing.
The man is described as white with short blond hair, possibly fair, and about 6ft tall with a slim build.
Police say a half-hour phone call was made from the suspect's Portuguese mobile phone between 7.30pm and 8pm, around an hour before Madeleine is believed to have gone missing.
A statement from German authorities added there is evidence to suggest either a dark coloured Jaguar XJR 6 or a white and yellow early 1980s VW T3 Westfalia was used to commit the crime.
Scotland Yard said the man was driving the vehicle in the Praia da Luz area in the days before Madeleine’s disappearance and is believed to have been living in it for days or weeks before and after May 3.
The Jaguar had a German number plate and was seen in Praia da Luz and surrounding areas in 2006 and 2007.
The day after Madeleine went missing, the suspect got the car re-registered in Germany under someone else’s name, although it is believed the vehicle was still in Portugal.
Police are appealing for anyone who may have seen the camper van in or around Praia da Luz on the night Madeleine went missing, the days before or weeks after, to contact them.
Both vehicles have been seized by German police.
Det Chief Insp Mark Cranwell, who is leading the Met's investigation, told reporters on Wednesday he was taking the “really unusual” step of releasing two mobile phone numbers as part of the appeal.
The first, (+351) 912 730 680, is believed to have been used by the suspect and received a call from another Portuguese mobile, (+351) 916 510 683, while in the Praia da Luz area, starting at 7.32pm and ending at 8.02pm on the night of May 3, 2007.
Madeleine is believed to have disappeared between 9.10pm and 10pm that evening.
The caller, who is not thought to have been in the Praia da Luz area, is not being treated as a suspect, but is said to be a “key witness” in the case.
Watch ITV News Correspondent Robert Moore's report on the disappearance of Madeleine McCann in May 2007:
“Any information in relation to these mobile numbers during the spring and summer of 2007 could be critical to this investigation,” said Mr Cranwell.
“Some people will know the man we are describing today, the suspect in our investigation.
"I’m appealing to you directly.
“You may know, you may be aware of some of the things he has done.
"He may have confided in you about the disappearance of Madeleine.
“More than 13 years have passed and your loyalties may have changed.
“This individual is in prison and we are conscious that some people may have been concerned about contacting police in the past. Now is the time to come forward.
“I’m appealing to you to contact us, or the German authorities or the Portuguese authorities.
“I should be very, very clear on this – while this male is a suspect, we retain an open mind as to his involvement.”
In a statement released on Wednesday, the BKA said: “The suspect lived more or less permanently in the Algarve between 1995 and 2007.
"For several years, he lived in a house between Lagos and Praia da Luz, among other places.
"He had several occasional jobs, among other things in the gastronomy business, in the Lagos area in this time period.
“In addition, there is information suggesting that he also earned his living by committing criminal offences, such as burglaries of hotel complexes and holiday flats as well as trafficking in narcotic drugs.
The suspect is believed to have lived at this house in the Praia da Luz area:
“Furthermore, the suspect was sentenced on numerous occasions to prison terms for sexual abuse of children in the past. This fact is probably not known to most of the contact persons.”
The BKA statement said officers believe others could have “concrete knowledge” of the crime.
“There is reason to assume that there are other persons, apart from the suspect, who have concrete knowledge of the course of the crime and maybe also of the place where the body was left. We explicitly ask these persons to contact us and provide information.”
A statement from Madeleine’s parents, read by Det Chief Insp Cranwell said: “We welcome the appeal today regarding the disappearance of our daughter Madeleine.
“We would like to thank the police forces involved for their continued efforts in the search for Madeleine.
“All we have ever wanted is to find her, uncover the truth and bring those responsible to justice.
“We will never give up hope of finding Madeleine alive, but whatever the outcome may be, we need to know as we need to find peace.
“We will be making no further comment in relation to the appeal today.
“We would like to thank the general public for their ongoing support and encourage anyone who has information directly related to the appeal to contact police.”
The Operation Grange incident room can be contacted via 0207 321 9251 or firstname.lastname@example.org