Fresh doubts have been raised over the reliability of crucial evidence given in a double murder case following allegations that the person who gave it lied.

Michael Stone has been behind bars for almost two decades - serving three life sentences for the deaths of Lin Russell and her six-year-old daughter Megan in 1996. He was also convicted of the attempted murder of Lin's other daughter Josie, who was nine at the time.

The family were tied up and beaten with a hammer, along with their pet dog, on a lonely country lane in Kent, and only Josie survived.

Stone has always claimed he's not guilty, maintaining "I'm an innocent man" but two trials and two appearances at the court of appeal found otherwise.

No forensic evidence or identification since the murders has ever linked Stone to the crime scene near the village of Chillenden in Kent.

In a new development to what has been dubbed one of Britain's most notorious crimes, a friend of the man whose evidence was crucial in putting Stone behind bars has come forward to allege the evidence given was a lie.

Fellow convicted murderer Damien Daley told the courts during Stone's trial that he had confessed to the Russell murders through a drainpipe while the pair were in neighbouring cells while on remand.

It was this claim from Daley that the judge at the trial said the jury either had to believe or Stone must be acquitted.

Now nearly 21 years after the murders, an old family friend of Daley - Peter Sinclair - has claimed that Daley told him he was going to lie before he gave evidence in court.

Stone has also told ITV News Correspondent Richard Pallot, in a letter written from his high security prison, that he is "completely innocent".

He wrote: "I categorically confirm that on 09/07/1996 I was in the Medway Towns (in Kent) all day and most certainly I did not go to Chillendon that day.

"I have been held in prison for 19 years for a crime I am completely innocent of."

Kent Police say they are "not looking for anyone else in connection with the case in which Stone was convicted".

Josie Russell, who has made a remarkable recovery from the hammer attack, and her father Shaun have said they do not wish to make comment on Stone or the murders of their family members.