A new suspect has emerged in the investigation into the disappearance of Madeleine McCann.
The focus on him is the latest in a series of twists and turns in one of the most high-profile missing person cases in recent history, which saw the three-year-old disappear from a holiday apartment in the Portuguese resort Praia da Luz in 2007.
Sky News crime correspondent Martin Brunt has been on Christian B's trail in Portugal and Germany to find out more about him.
Among the inmates of Kiel's high-security jail in northern Germany, there is one prisoner who has become the most notorious of all. He's isolated for his own protection and allowed to exercise, alone, for only one hour a day.
With publication of his full name restricted under German privacy laws, he is only known as Christian B - but there can't be many who don't know exactly who he is.
He's German, aged 43, and what used to be called a drifter - flitting between Germany and Portugal for many years and working a variety of odd jobs when he wasn't committing crimes.
It's three months since the convicted paedophile, rapist and drug trafficker was identified as the latest suspect in the Madeleine McCann case, suspected of abducting and killing the little British girl who vanished 13 years ago during a family holiday in Portugal.
The case against him is circumstantial - he is a convicted paedophile, he lived in the area, and on the night she disappeared, his mobile phone was in use nearby. The next day he changed the registration of one of his vehicles.
As investigators continue to search for the vital evidence they need to charge him with Madeleine's abduction, Christian B is now the subject of three new investigations in Portugal.
I've covered the Madeleine McCann mystery since she disappeared. Over the years I've reported on various suspects, all of them eventually ruled out, but I wanted to find out, have they got the right man this time?
The prosecutor versus the defence lawyer
I've travelled far and wide across Europe covering this case. The first stop on my latest journey is Braunschweig in central Germany to meet the man in charge of the investigation into the connection between Christian B and Madeleine.
Braunschweig prosecutor Hans Christian Wolters believes Madeleine is dead and Christian B killed her, though he won't reveal why he is so certain.
But three months after he launched a global public appeal for new, vital clues, he still hasn't got enough evidence to charge him.
At his office near the reconstructed medieval town centre, Mr Wolters said: "We have found nothing in the past three months to make us think we've got the wrong suspect, but the evidence we have now is the same we had when we made our first appeal on 3 June.
"We have had hundreds of calls - 400 to us and hundreds to Scotland Yard - but we haven't got the information we need to charge Christian B. But there are some clues that make us hopeful our investigation will be more successful," he added.
The German, British and Portuguese authorities have targeted Christian B for three years, since a criminal associate of his told police he had effectively confessed to him, in a bar conversation, that he had abducted Madeleine.
But they've been unable to find forensic evidence that links the suspect to the victim, even though they have examined the VW camper van and Jaguar car he was driving at the time.
Mr Wolters said: "There is no forensic evidence, but it is not necessary to have forensics to charge our suspect. We just need more evidence, but I can't say what it is we are looking for though there are different possibilities. Maybe a witness, a photo or a video."
He added: "Someone asked me if we had found Madeleine's clothes. If we had found something like that it would be great for our investigation, but it's not true."
The prosecutor described as "speculative" a recent two-day dig at Christian B's former home outside Hanover, saying: "We are checking everywhere he lived and we know from his past that he liked to bury things like the USB computer sticks that were found in a previous investigation.
"I can't tell you what we found."
Mr Wolters said the Portuguese police had searched some wells on information supplied by the Germans and there had been other searches that were not publicised.
The suspect is imprisoned 300km away in the port of Kiel, where he's nearing the end of a sentence for drug trafficking.
His lawyer Friedrich Fulscher insists the prosecutor is wrong and Christian B isn't the man who abducted Madeleine, though he hasn't been shown the evidence against him.
In his spacious office, 2km from the prison, Mr Fulscher said: "I don't know any more after three months because I can't look in the prosecutor's files. He still hasn't told us anything. It isn't fair for him to keep accusing Christian B of killing the girl without telling us the evidence he has.
"There is a legal principle, that both sides have to have the same weapons. It's time for the prosecutor to show his cards, because he is prejudging my client in public without giving him the chance to go into action."
He accused the prosecutor of turning the public against Christian B and is worried about the suspect's future if he is never charged over Madeleine.
Mr Fulscher said: "If he is not charged there will be no chance for him to lead a normal life anywhere in the world, because everyone will connect him to the case. He should have the right to go back into society and be rehabilitated."
The rape trial
Christian B moved to Portugal in 1995 and flitted between the Algarve coast and Germany for many years. In Portugal he had a reputation as a prolific burglar, but it was also the scene of his most serious crime.
In 2005, wearing a balaclava mask, he broke into the beachside villa of an elderly American widow in Praia da Luz, dragged her upstairs to a bedroom, tied and gagged her, then assaulted and raped her. Police found no fingerprints or DNA.
He wasn't convicted until December 2019, when he was tried in Germany, where he was already serving a sentence for drug trafficking. He was jailed for seven years, though the sentence was postponed pending his appeal over the legality of his extradition from Italy.
Mr Fulscher, who didn't represent him at the rape trial, believes Christian B was convicted on thin prosecution evidence.
The most damning was that one of his hairs was found in his victim's bed, though the suspect suggested it may have been carried there by a cat he stroked regularly outside the villa which was on his route home from the beach.
The other main evidence was a statement from the victim who did not appear in court and the testimony of two former criminal associates, one of whom is an informant against him in the Madeleine McCann case.
In fact, Christian B became the main suspect in the Madeleine case when the witness called police to tell them he had confessed to him in a bar. At the time, the informant is thought to have been in jail in Greece.
Mr Fulscher said: "Both the main witnesses are the worst witnesses. They are criminals, accusing each other of drugs and alcoholism, having Alzheimer's and telling lies. You can't believe anything they say, yet the court said they were reliable witnesses.
"One of them was sentenced in Greece for seven years for human trafficking and I know noticeable is that he got out of prison really quickly in Greece. Not even two years. Why he was released after such a time, there may be different explanations. Maybe he got some benefit because he helped to solve things."
Crucial evidence from the two witnesses was their story of breaking into Christian B's house and stealing homemade videos of him raping several victims, though not the American widow.
But the court was not shown the videos and one of the witnesses told the judges the tapes had been destroyed in a caravan blaze.
Mr Fulscher said: "What makes it worse is that the witnesses weren't questioned for long. The whole case took only three days.
"I would have spent three days just questioning one of the witnesses. The videos were not shown in court, where they are is a mystery."
His lawyer says he was later told the videos had been sold to a man who ran a remote farm retreat in Portugal.
I drove for more than an hour in scorching heat into the hills above the Algarve coast, along twisting roads and dusty tracks to the farm that sits on a mountain top with glorious views across the Alentejo region.
But it was a fruitless journey, because the man denied any knowledge of the tapes and the witnesses. And he wasn't pleased to see me.
Investigators seem determined to prosecute Christian B for other crimes, even if they don't find the evidence they still need to charge him with the abduction of Madeleine McCann.
That's illustrated by the case of Hazel Behan, a young Irish holiday rep who was raped in her apartment in Praia da Rocha on the Algarve coast in 2004.
When she read in June that Christian B had been convicted for the 2005 rape of an elderly American widow in a nearby resort, she asked Portuguese police to reinvestigate her unsolved case.
Her description of her ordeal bore remarkable similarities to the American victim's rape a year later.
Portuguese detectives went back through their files, but a decision has only just been made not to reopen the investigation.
In a letter to Sky News, the prosecutor at Portimao court wrote: "The investigation will not be reopened because of the statute of limitations."
In Portugal, some criminal cases cannot be reinvestigated after 15 years.
But we've also learned that the authorities in Germany - where the statute of limitations for sex crimes is 20 years - are investigating the rape, with two witnesses we know of being asked to give statements to German investigators.
German prosecutor Hans-Christian Wolters said: "I cannot confirm right now officially that we have an investigation in that case, but we have an eye on it. Maybe we are doing an investigation."
Christian B's lawyer Friedrich Fulscher said: "Hazel B has said the perpetrator had a noticeable tattoo or birthmark on his right buttock, but you can exclude Christian B because he doesn't have anything like that."
Two more cases being re-examined because of suspicions around Christian B are alleged sexual exposure to young girls in Portugal.
A man exposed himself to a 10-year-old German girl on Salema beach a month before Madeleine vanished in 2007. The girl's mother contacted police recently after seeing Christian B's photograph in the media.
And three years ago he was arrested for a similar allegation at a village festival in Sao Bartolomeu de Messines in the hills above the coast.
Instead of being charged, he was extradited to Germany where he was wanted for a similar crime, but now police are planning to prosecute him and are re-interviewing four young victims and witnesses.
Mr Wolters said: "If we find in our Madeleine investigation hints about other crimes then we have to look at those. It doesn't mean we are not making progress in the Maddie case."
Defence lawyer Mr Fulscher said: "I also think they're trying anything to sentence Christian B for other deeds… maybe they know they don't have enough in the Maddie case and they want to have the same result in a different way."
Suspects in the Madeleine McCann investigation have come and gone over the years since she vanished after being left sleeping in the family's holiday apartment in Praia da Luz in May 2007.
Just before paedophile Christian B became the main suspect in the Madeleine McCann case, police were pursuing a quite different theory.
It focused on another suspect in another country and involved a delicate undercover operation. I don't know if that investigation is entirely over, but I think it would be wrong to describe Christian B as the only suspect in this case.
In fact, one source told me that Christian B may be no better a suspect for Madeleine's abduction than two other principle targets.
They are the unnamed suspect, who may still be the subject of an undercover operation, and Euclides Monteiro, a sacked Ocean club waiter and thief who died two years after Madeleine vanished and was later eliminated from the inquiry.