William Dale Archerd married seven times in 15 years, a rare feat by any standards. He kept up a steady supply of wives because of their habit of dying – helped, it should be said, by his habit of killing them.

From an early age he wanted to be a doctor. It was an appropriate career choice, because everywhere he went he carried a hypodermic needle and a bottle of insulin. For Archerd, though, these were not intended as agents of healing, but of agonising death.

He first came in contact with his killing tools while working as an attendant in a state mental hospital. In the 1940s insulin injections were given to patients to help them out of their mental relapses.

But Archerd discovered that giving large doses of the drug to someone who has no need of it might cause death.

That it would be agonising death didn’t worry him one bit…