A former Northern Ireland detective who has played a central role in the investigation into the disappearance of Madeleine McCann said the latest developments in the case bring him such hope he believes an end could be in sight for her heartbroken family.
London and German police have identified an unnamed suspect who was in the Praia da Luz resort on the Algarve coast at the time the three-year-old vanished on May 3 2007.
"This is a substantial and very significant lead," Jim Gamble told ITV's This Morning.
Mr Gamble was the senior child protection officer in the UK's first investigation into the disappearance of Madeleine.
The Bangor man is one of the UK's most experienced and outspoken experts on the safeguarding of children online.
He now runs the Belfast-based INEQE Group which continues to spearhead the battle to make the online world safer for children.
Police are treating the disappearance of Madeleine as murder.
He said the developments on Wednesday evening had given him more hope than in the last 13 years of a breakthrough.
After his 2010 review into the case it was "critical" the expertise of the Metropolitan Police was brought on board, he said.
This is about what happened to Madeleine McCann and hopefully we are at the end of this journey.Jim Gamble
He said the evidence, from what police have released so far was circumstantial but appeared on the face of it to be strong.
"So you will look at a person's opportunity to commit a crime, the preparation they may have committed in their subsequent conduct," he continued.
"You have an individual that - we are told - has committed similar offences, the age range of his previous offences are quite wide.
"We know he was in proximity of the crime and this circumstantial evidence is further strengthened by the phone call, cell site analysis that puts his phone in a particular place at a particular time and in immediate proximity to the timeline of the offence.
"Then you look at more circumstantial evidence, in other words the subsequent conduct of an individual.
"The day after we are told that a number plate of a car is changed. So all of that when you bring it together makes him a very, very significant person of interest."
The former head of RUC Special Branch was awarded the Queen's Police Medal in 2008. He described as "useful" the Met sharing information.
"But not over sharing," he stressed.
"This jigsaw is coming together there are some pieces missing and if the public are now prompted, if there is someone who has held something back suddenly realises how important the little piece of information they have is and comes forward they might bring those last pieces together."
He added: "It is important the Met don't share too much to put words in people's mouths because the evidence has to be sufficiently independent in order to be put before a court."
German police said the suspect has numerous convictions for child abuse and drugs and is currently in jail. He made money burgling holiday makers apartments. They believe he may have taken Madeleine while breaking into the McCann's accommodation.
He came to their attention after discussing the case in an internet chat room. Two properties, near where the McCann's were staying have become central to the investigation.
Mr Gamble continued: "The truth is the beginning of this investigation was bungled - that's not criticism of the police. It is that these cases are very rare and there are very few police services with the capabilities and capacities to deal effectively with them."
He said evidence was not collated together and mobile phone analysis may not have been examined. Some leads he claimed may have slipped through the net.
"One of the recommendations we made was for the Met Police - I think the finest detectives in the world - had to be involved.
"And what we saw once they did was the painstaking approach to go through what was a chaotic collection of information and generate 600 lines of enquiry and narrow each one down.
"What we are seeing here is the outcome from long hard hours put in from detectives.
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.Gerry and Kate McCann
"This is like a jigsaw puzzle. You empty a box on the table, some bits might fall on the carpet others can't be put in place until you have the context around them.
"And credit to the Home Office because they have continued to fund this investigation .. there have been lots pushing for funding to stop and that can not happen when they are still lines of enquiry.
"This is about what happened to Madeleine McCann and hopefully we are at the end of this journey."
Gerry and Kate McCann have said they will “never give up hope” of finding their daughter alive in their quest to “uncover the truth”.
In a statement they said: “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.”
Ever since her disappearance, Madeleine’s parents have consistently vowed to keep searching for their daughter.
Clarence Mitchell, who was a spokesman for the McCann family, said there would be mixed emotions for the McCanns given the seemingly endless turns the case has taken over the past 13 years without little substance.
He also slammed those online social media trolls who have brought "misery" to the family.
This feel more significant," he said, "they will not say more other than the short statement as they want the focus to be on the investigation.
"They just want to know what happened, they need, as they say, peace. And if this leads to that, they that can be the only positive aspect to all this.
"One always wants to know what happened a love one... it is hard to talk about hope and optimism given this man has an awful record.
"They [the trolls] need to have a long hard look at themselves."