A major breakthrough has been announced in the disappearance of Madeleine McCann.
A new prime suspect who was living in the Portugal seaside resort where the three-year-old vanished 13 years ago has been identified by police in Germany.
Here is what we know so far:
He is a convicted sex offender
German police have not named the prime suspect, but have said he is child sex offender.
The man, who has not been named, is white with short blond hair, possibly fair, and about 6ft tall with a slim build at the time the three-year-old disappeared on May 3, 2007.
Christian Hoppe, from Germany's Federal Criminal Police Office (BKA), told the country's ZDF television channel the 43-year-old is serving a prison sentence for a sex crime and has two previous convictions for "sexual contact with girls".
German newspaper Braunschweiger Zeitung reported the suspect was carrying out a seven-year prison sentence for the rape of a 72-year-old American woman in Portugal in 2005.
He would have been 30 at time of disappearance
Police are hoping that the appeal will bring forward witnesses in Portugal at the time.
The UK officer leading the case, Detective Chief Inspector Mark Cranwell, said: "He is a German national, he's currently in a German prison for an unrelated matter. He's white, he's about six foot in height.
"He's 43 now. At the time he was 30, but he could have looked aged somewhere between 25 and 32.
"There may be people in the past, who have been quite fearful of coming forward to the police, and my message is to anybody that has information.
"Did, did he speak to you in confidence, and tell you what happened that night? And that is my message and the message really is associated with fact he is currently in prison.
"And this might be a good time, this is a good time, to come forward and talk to, whether it's the UK police, whether it's the German police or the Portuguese police."
Disappearance is being treated as murder
The Braunschweiger Zeitung newspaper said the suspect was convicted of the offence in Braunschweig district court in December last year.
Germany's Federal Criminal Police Office Christian Hoppe said German police have not ruled out a sexual motive for the alleged crime against Madeleine, which is being treated as murder by the BKA.
He 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.
Others believed to be involved
The police appeal in Germany say that other people with knowledge of crime could be known
The appeal said: "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."
Suspect was living in Portugal 13 years ago
The German national is known to have been in and around Praia da Luz on the Algarve coast at the time Madeleine vanished, while on holiday with her parents, Kate and Gerry McCann, and her twin siblings Sean and Amelie.
A half-hour phone call was made to his Portuguese mobile phone around an hour before Madeleine is believed to have gone missing.
The suspect, who is in prison in Germany for an unrelated matter, has been linked to an early 1980s VW T3 Westfalia camper van - with a white upper body and yellow skirting, registered in Portugal - which was pictured in the Algarve in 2007.
Scotland Yard said he 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.
DCI Cranwell said: "The [campervan] colour tone is quite distinctive is quite old and probably described as a bit beaten up but it was a white upper body, and a yellow sort of lower body.
'We know that that vehicle was in the area. Certainly the days leading up to it. And the week afterwards, I'm really interested if anybody can place that vehicle in certain areas or anywhere around Praia da Luz or surrounding areas. And did they see a German male, with that vehicle, was there anything suspicious about that?"
Car also linked to the case
He has also been linked to a 1993 Jaguar XJR6 with a German number plate 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.
Both vehicles have been seized by German police.
Joint appeal launched in England, Germany and Portugal
Scotland Yard is launching a joint appeal with the Federal Criminal Police Office of Germany (BKA) and the Portuguese Policia Judiciaria (PJ), including a £20,000 reward for information leading to the conviction of the person responsible for 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.
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.
Detective Mr Cranwell, said: "It's more than 13 years since Madeleine went missing and none of us can imagine what it must be like for her family, not knowing what happened or where she is.
"Following the ten- year anniversary, the Met received information about a German man who was known to have been in and around Praia da Luz.
"We have been working with colleagues in Germany and Portugal and this man is a suspect in Madeleine's disappearance.
"The Met conducted a number of enquiries and in November 2017 engaged with the BKA who agreed to work with the Met.
"Since then a huge amount of work has taken place by both the Met, the BKA and the Polícia Judiciária.
"While this male is a suspect we retain an open mind as to his involvement and this remains a missing person inquiry.
"Our job as detectives is to follow the evidence, maintain an open mind and establish what happened on that day in May 2007.
"Please contact us without delay so we can get answers for Madeleine's family."
What Madeleine's parents say
A statement from Madeleine’s parents, read by Det Chief Insp Mark 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.”