In June 1999 the people of the village of Clydach, South Wales, woke up to horrific news: a family of four, a mother, Mandy Power, her two young daughters and their grandmother had all been beaten to death. Their house had been set on fire in an attempt to destroy the evidence and cover up murder.

Within days, the case became even more notorious when it emerged that the dead woman, Mandy Power, had been having a lesbian affair with a married woman - married to a police officer in the Force which had to investigate the murders.

For South Wales Police this was the "Murder from Hell": not just because one of their own officers was a suspect, but because they were under intense pressure to get this case right after a series of miscarriages of justice going right back to the 1980's.

Innocent people had spent years in jail while killers walked free.

In the summer of last year, David Morris, a local builder's labourer with a criminal record for drunkenness and violence was jailed for life for the murders. But there was no forensic evidence linking Morris to the crime and his family protest that his is the latest in a long line of miscarriages of justice in South Wales.

"Panorama" investigates and finds similarities between this case and earlier miscarriages: similarities which carry disturbing echoes of past wrongdoing by South Wales Police.