And at the heart of all of them is a simple question – did the man convicted of the crime actually do it?

Kent Police’s only contribution – other than historic clips and comments from former employees – is merely a submitted statement at the end of the programme insisting that Stone has been tried and found guilty on two occasions. But the evidence remains elusive – the CCRC unmoved. Stone’s legal team insist they want exhibits from the murder scene re-examined, forensically. They believe it could result in DNA being identified which could prove the killer. Josie Russell won a Children of Courage award following her ordeal Hulton Archive/Getty Images Detectives initially did not suspect Constance Kent of killing her brother — attention focused on the nanny and the boy’s father. And it is the long-held anxiety over the strength of evidence which convicted him which has prompted the latest TV documentary on the case.

There would be an increased police presence in the area while investigations into the circumstances took place, the force added. Stone was proven to be in Medway four hours before the crime took place (he signed a timed receipt in a branch of Cash Convertors) and he did not closely resemble the photofit circulated by Kent Police, as described by a witness who saw a man exit the lane the murders took place in a car. Five years later, Constance Kent confessed to the crime. She had acted “quite alone,” Constance promised, but she never expressed a motive for the murder beyond that it was committed “not out of jealousy.” Anyone with information should call 999, quoting reference number 23-1922. For any other information that may assist the investigation call 01843 222289, quoting the same reference number. Formal identification has not yet taken place, however, the family of a 54-year-old woman reported missing from Upstreet on Wednesday 23 August are aware. The death is being treated as suspicious and on 24 August a man in his 20s from Margate was arrested on suspicion of murder.”

A full DNA profile, which police believe belongs to the killer, was created from crime scene evidence in 2008 but "a missing piece of the jigsaw has yet to be traced". The impact on the people involved in those first moments is both harrowing and clearly emotional all these years later. Michael Stone has been behind bars since he was first arrested in 1997 Hulton Archive/Getty Images Constance Kent was 16 years old when her brother’s body was found behind her house. Claire Knights was last seen in Upstreet near Canterbury on Wednesday. It is believed she was walking her dog in the village to Minnis Bay in Birchington, where she was reportedly seen that afternoon. As Jim Fraser, head of forensic investigations at Kent Police at the time, says: “Could he have done it? Yes. Did he do it? That’s a completely different question.”Yet it was there his cell neighbour, Damien Daley – held on charges of arson and robbery – claimed to have heard Stone admit to the crimes again. His testimony, would, eventually, see Stone jailed. Twice.

In just April this year, the parents of Wendy Knell asked the public for help to establish the identity of their daughter's killer. The full list has been revealed by Kent Police and, despite many fresh appeals as well as more modern forensic techniques, the killers of these 40 people have never been caught. A 47-year-old woman, also from Coulsdon, has also been arrested on suspicion of assisting an offender. All five remain in custody. The man who killed her is still on the loose and he is believed to be a serial killer who five months later targeted another young woman in the town, Caroline Pierce. The judge at Maidstone Crown Court instructed the jury that if they did not believe Daley’s testimony, Stone should be acquitted.Constance Kent went down in history as a cold, calculating teen killer. But the truth of what happened in Hill House Road the night Francis Kent died may remain a mystery. It was known as the Great Crime of 1860. On June 29, 1860, an unknown assailant murdered 3-year-old Francis Savile Kent in a brutal fashion.