Goncalo Amaral - a Portuguese officer - was part of the police investigation into Madeleine’s disappearance from a vacation home in Portugal’s Algarve region in May 2007, days before her 4th birthday.
In 2008, he published a book about the case, which he titled Maddie: The Truth About The Lie.
In this book, Amaral claims that Madeleine had died in the family’s holiday apartment in the Algarve.
He then went on to claim that they had faked her abduction to cover up the tragedy.
The book became a bestseller in Portugal, despite the fact that many of the country’s top detectives have insisted there’s no evidence to back up his claims.
Following the publication of the book, Amaral was sacked as head of the investigation.
After the McCanns took him to court over his book's claims, he was asked to pay them £395,000 in libel damages.
Kate and Gerry said at the time that they were “totally destroyed” by Amaral’s allegations, adding that they felt “ashamed” that they might appear to have been to blame for their daughter’s disappearance.
However, in April this year, Portuguese judges overturned the payout after he appealed the ruling.
Speaking to the Associated Press about the decision, Amaral’s lawyer said: “The appeals court decided that he had the right to do what he did. It said he can write what he wants.
“It absolved him, said he didn’t have to pay anything.”
In an online post, Amaral thanked his supporters after he won his appeal.
He said firmly: "None of this would have been possible without you."
However Kate and Gerry McCann are planning to contest the overturn and will now take the case to the country's Supreme Court.
To help Amaral with legal costs, some of his British supporters - labelled trolls by many - have set up a GoFundMe page.
They have, so far, raised £50K for the Portuguese detective.
The fundraising page was started by Leanne Baulch, a student of psychology from Birmingham, in April 2015.
The mother-of-one told The Daily Mail: “I set up the page to help him [Amaral] with his appeal because I felt he had suffered an injustice. His assets had been frozen so he had no way to defend himself.”
She added: "I'm not anti-Kate and Gerry McCann, I don't know what happened and I don't claim to know. But I do believe there are hard questions that need to be answered."
The page has since been closed down.
Madeleine McCann was three-years-old when she disappeared from her bed in a holiday apartment in Portugal in May 2007.
Maddy’s parents, Kate and Gerry, had left the little girl and her two-year-old twin siblings sleeping in their holiday home as they dined with friends at a restaurant 50 metres away.
They checked on the children throughout the evening, at roughly half-hour intervals, until Madeleine's mother discovered she was missing at 22:00.
Since then, they have campaigned tirelessly for information as to their daughter’s whereabouts.
It has been nine years since Madeleine McCann disappeared - and she would be 13-years-old this Thursday (12th May).
On 3rd May 2016, the anniversary of Madeleine’s disappearance, her parents shared a message on their Find Madeleine website.
It read: “As yet another anniversary comes around, we’d like to thank all our supporters for your continued help and commitment in the search for Madeleine, and the hope for her safe return.
“It has been a very long time but the investigation continues, information is still forthcoming and our hope and resolve continue. Until we have answers, until there is news, there will always be hope and we will continue to do everything we can to help find Madeleine.
“The charity Missing People is releasing the single I Hope on May 20 ahead of International Missing Children’s Day. Please support the charity to help all missing children and their families by downloading the song.”
Tragically, the couple are still no closer to finding out where Madeleine is - or what happened that fateful night in Praia Da Luz.
However, in a new interview, police officers have revealed that there is a chance that Maddy could be found alive - nine years after her disappearance.
Detective Chief Superintendent Mick Duthie, the head of Scotland Yard’s homicide squad told the Evening Standard: “There is ongoing work. There is always a possibility that we will find Madeleine and we hope that we will find her alive.
“That’s what we want and that’s what the family and the public want and that is why the Home Office continue to fund it.”
He added: “There is work that needs to be done still.”
It was recently revealed that Scotland Yard had been given more money to help with the Find Maddy investigation - but the funds came with a time frame.
They now look set to close the investigation in six months, whether or not they manage to track down the little girl.
Operation Grange will now continue until early October, until the extra £94,592 runs out.
Once the money is gone, Scotland Yard will have to end the five-year inquiry, which has cost £12 million already.
A Home Office spokesperson said: “Following a request from the Metropolitan Police Service, we have agreed to provide nearly £95,000 of further funding for Operation Grange.”
A Scotland Yard spokesperson said: “The inquiry has not reached a conclusion. There are still focused lines of investigation to be pursued.
“There are no immediate plans to reduce office numbers further at this time.”
You may also wish to read: