During the night of 6 August 1985, Nevill and June Bamber were shot and killed inside their Essex farmhouse along with their adoptive daughter, Sheila Caffell, and Caffell’s six-year-old twin sons, Daniel, and Nicholas.

Bamber, then 24, phoned the police to say Nevill had called him saying his daughter Sheila had “gone crazy and has the gun”. Initially, police believed that Sheila Caffell, diagnosed with schizophrenia, had fired the shots, and then turned the gun on herself.

But on 10 August, after the police ended their examination of the crime scene, a silencer was found in a gun cupboard at the farmhouse. It was later said to contain blood belonging to Caffell.

In 2018 a  ...