Mone, now 67, and McCulloch killed Nursing Officer Neil MacLellan and patient Iain Simpson inside the hospital’s social club using home-made weapons, and escaped by climbing over the fence.
They then fatally stabbed 27-year-old PC George Taylor on the road outside, and seriously injuried another officer before making off with the police car.
Now, in letters to be published in a book: “Carstairs: Hospital for Horrors” Mone is reported to have described that night, November 30 1976, as a a “nightmare of shattered dreams and grotesque, maniacal butchery”.
And he apparently speaks of McCulloch hacking Neil MacLellan to death - after Mone had sprayed paint thinner into the nurse’s eyes - and of McCulloch repeatedly hitting the fellow patient Iain Simpson with an axe.
In the inquiry in the aftermath of the killings, Sheriff R. Reid gathered the evidence of that initial struggle, which included Mone picking up a garden fork and attacking Mr Simpson with it until Mr Simpson collapsed, then going to help McCulloch who was fighting with Mr MacLellan.
In his report, the Sheriff said that Mr MacLellan, who was 46, had “acted with great courage and in accordance with the highest tradition of the nursing service”.
The evidence was that McCulloch had pushed Mone outside to keep watch, then had gone back in and murdered Mr MacLellan and the patient with the axe.
Outside the hospital, Mone lay on the road pretending there had been an accident, attacking the police officers who stopped.
Mone and McCulloch drove away in the police car, crashing it on the A702, and then attacking the occupants of a van who stopped to help - one was hit on the head and the other stabbed a number of times.
The escapers took their van, driving through Biggar, before getting it bogged down off the road. They then continued with a car taken from a nearby farm, but that too went off the road before Carlisle, and the police caught up with them.
Mone is still a prisoner. The book, written by journalist David Leslie, looks at the crimes of others held in the secure hospital.
But the letters of Mone are bound to stir up strong feelings in all those affected by the break-out –the families of those killed, the staff who worked with the patients, and those living in the wider area who were troubled by the security and the fears for the hospital alarm system.