The Firkins were found guilty of battering the couple to death

Robert and Lee Firkins were jailed for life for murdering Graham Fisher, 60, and his wife Carol, 53, in 2003.

The couple were found bludgeoned and shot at their home near Wadebridge.

Court of Appeal judges sat on Friday to discuss a letter which raised questions about the reliability of a key witness in their trial.

A jury at Exeter Crown Court found the brothers, of Weston-super-Mare in Somerset, guilty of the murders at the Perch Garage in November 2003.

But in February this year they were granted an appeal against their conviction at the Court of Appeal in London.

The Fishers were shot before and after being bludgeoned to death

Lord Justice Scott Baker at the Court of Appeal said on Friday there should be an investigation into the reliability of evidence given by a prison inmate who testified that Robert Firkins once bragged: "Watch Crimewatch and you will see my work."

The witness, who cannot be named by court order, had shared a cell with Robert Firkins.

Lord Justice Scott Baker, sitting with two other judges, said the case was in court due to a recent letter written by the witness, who had given "important evidence at trial - the substance of which was that one of the applicants confessed to having committed the murders".

The judge added: "Putting matters as neutrally as possible, this letter raises issues as to the reliability of his evidence at trial.

"The court needs to know in more detail what it is that he wishes to say; he needs to be seen and a full witness statement needs to be taken from him."

He directed that the investigation and witness interview be undertaken by a senior detective with a police force other than the Devon and Cornwall Constabulary, which carried out the initial murder probe.

Mrs Fisher's brother Nigel Edwards said afterwards: "We are shocked and despondent.