'A volley rings out - a nervous volley it is true, yet a volley.

Before the fatal shots are fired I had called the battalion to attention. There is a pause, I wait.

I see the medical officer examining the victim. He makes a sign, the subaltern strides forward, a single shot rings out.

Life is now extinct ... We march back to breakfast ... This is war.' Brigadier-General Crozier describes an execution he has ordered of a man who fell asleep on sentry duty.

Much has been written about the 346 men who were executed in WW1 but there is usually only a passing reference to those who took part – the members of the firing squad, the officer in charge, the medical officer and the padre. What are their stories?

Through extensive research, David Johnson explores how they were selected and how they were treated before, during, and after the executions, and why there were so many procedural variations in the way that the executions were conducted.