Admissions of murder do not come more startling than that made by one-time butler to the aristocracy Roy Archibald Hall. In his memoirs he wrote, describing the death of his first victim: “I shot him in the head and for a moment he just stood there, staring. I thought, ‘I’ve missed the bastard.’

“But then, slowly, a trickle of blood appeared at the left corner of his mouth. It trickled delicately down his chin. And then he fell. Walking over to him, I shot him in the chest.

“‘See! See what you’ve made me do. You stupid, stupid, greedy bastard.’

“I shot him again. His eyes were still open. ‘It’s all right for you, your troubles are over. Mine are just beginning.’ I shot him again.”

The scene was a Scottish moor in 1977. The victim was David Wright, a 30-year-old petty thief and Hall’s double-crossing lover. Four more people were later to die in a killing spree that made Roy Archibald Hall unique. Who else could claim they had also killed their mistress, their half-brother, and a former Labour minister and his wife, all in just six weeks?